אהבה
הלכות תפילין ומזוזה וספר תורה
פרק ג
Ahavah
Tefillin, Mezuzah, and Sefer Torah
Chapter 3

Halacha

הלכה א
שְׁמוֹנֶה הֲלָכוֹת יֵשׁ בְּמַעֲשֵׂה הַתְּפִלִּין כֻּלָּן הֲלָכָה לְמשֶׁה מִסִּינַי. וּלְפִיכָךְ כֻּלָּן מְעַכְּבוֹת וְאִם שִׁנָּה בְּאַחַת מֵהֶן פָּסַל. וְאֵלּוּ הֵם. שֶׁיִּהְיוּ מְרֻבָּעוֹת. וְכֵן תְּפִירָתָן בְּרִבּוּעַ. וַאֲלַכְסוֹנָן בְּרִבּוּעַ עַד שֶׁיִּהְיֶה לָהֶן אַרְבַּע זָוִיּוֹת שָׁווֹת. וְשֶׁיִּהְיֶה בָּעוֹר שֶׁל רֹאשׁ צוּרַת שִׁי״ן מִיָּמִין וּמִשְּׂמֹאל. וְשֶׁיִּכְרֹךְ הַפָּרָשִׁיּוֹת בְּמַטְלִית. וְשֶׁיִּכְרֹךְ אוֹתָן בְּשֵׂעָר מֵעַל הַמַּטְלִית. וְאַחַר כָּךְ מַכְנִיסָן בְּבָתֵּיהֶן. וְשֶׁיִּהְיוּ תּוֹפְרִין אוֹתָן בְּגִידִין. וְשֶׁעוֹשִׂין לָהֶן מַעְבֹּרֶת מֵעוֹר הַחִפּוּי שֶׁתִּכָּנֵס בָּהּ הָרְצוּעָה עַד שֶׁתְּהֵא עוֹבֶרֶת וְהוֹלֶכֶת בְּתוֹךְ תּוֹבָר שֶׁלָּהּ. וְשֶׁיִּהְיוּ הָרְצוּעוֹת שְׁחוֹרוֹת. וְשֶׁיִּהְיֶה הַקֶּשֶׁר שֶׁלָּהֶן קֶשֶׁר יָדוּעַ כְּצוּרַת דָּלֶ״ת:
כסף משנה
1.
There are eight requirements in the making of tefillin. All of them are halachot transmitted to Moses on Mount Sinai1In Chapter 1, Halachah 3, the Rambam mentioned that there were ten requirements for tefillin that were communicated as "halachot transmitted to Moses on Mount Sinai." The first two involve the actual composition of the tefillin. They, and the other laws involving that subject, were discussed in the first two chapters. Now the Rambam discusses the requirements involved in making the tefillin's compartments and straps. and, therefore, it is necessary to fulfill them all. If one deviates with regard to any of them, the [tefillin] are unacceptable.2Though a "halachah transmitted to Moses on Mount Sinai" is not written in the Torah itself, it is as binding upon us as those laws which are stated explicitly. They are:

a) The tefillin must be square3There is a homiletic dimension to this requirement. Nothing is naturally square. Thus, this shape alludes to man's power of achievement. Wearing tefillin on our heads and opposite our hearts implies that we should exercise our powers of achievement when our minds and hearts are tied to God's mitzvot.
The base of the tefillin must also be square. The Shulchan Aruch (Orach Chayim 32:39) states that this is also a halachah transmitted to Moses on Mount Sinai.
Note Shulchan Aruch HaRav 32:59 and the Mishnah Berurah 32:181, which state that since the squareness of tefillin is a halachah transmitted to Moses on Mount Sinai, the tefillin must remain square at all times. If over the course of time, their shape changes, they may no longer be used.
and must be sewn closed in a square.4See Halachah 10. [Both] diagonals5of the square on the top and the base of the tefillin must be equal,6The commentaries cite Sukkah 8a, which states that the diagonal of a square is approximately 1.4 times the length of one of its sides. and thus all four angles will be equal.7Each one being 90 degrees. See Halachot 2 and 4.

b) The leather of the head [tefillin] should have a shin embossed on both its right and left sides.8See Halachah 2.

c) The passages should be wrapped in fabric.9See Halachah 8.

d) A hair should be wound around that fabric. Afterwards, they should be placed in their compartment.10See Halachah 8.

e) They should be sewn [closed] with the sinews [of an animal].11See Halachot 9-10.

f) The leather compartment in which they are placed should have a place for the straps to pass through so that they can be moved through the [tefillin's] handle.12See Halachot 3-4.

g) The straps should be black.13See Halachot 14.

h) The knot with which they are tied should be the renowned knot that is formed like a dalet.14See Halachah 13. Note Shabbat 62a, which states that the knot of the arm tefillin, which is shaped like a yud, is also a halachah transmitted to Moses on Mount Sinai.

הלכה ב
כֵּיצַד עוֹשִׂים תְּפִלִּין שֶׁל רֹאשׁ. לוֹקְחִין עֵץ מְרֻבָּע אָרְכּוֹ כְּרָחְבּוֹ וּכְגָבְהוֹ. וְאִם הָיָה גָּבְהוֹ יוֹתֵר עַל רָחְבּוֹ אוֹ פָּחוֹת מִמֶּנּוּ אֵין בְּכָךְ כְּלוּם. וְאֵין מַקְפִּידִין אֶלָּא עַל אָרְכּוֹ שֶׁיְּהֵא כְּרָחְבּוֹ. וְחוֹפְרִין בּוֹ שְׁלֹשָׁה חֲרִיצִין כְּדֵי שֶׁיֵּעָשֶׂה לוֹ אַרְבַּע רָאשִׁים כְּגוֹן זֶה:

וְלוֹקְחִין עוֹר וּמַרְטִיבִין אוֹתוֹ בְּמַיִם וּמְשִׂימִין בּוֹ אֶת הָעֵץ וּמַכְנִיסִין אֶת הָעוֹר בֵּין כָּל חָרִיץ וְחָרִיץ וּמְכַמְּשִׁים אוֹתוֹ וְהוּא רָטֹב מִכָּאן וּמִכָּאן עַד שֶׁעוֹשִׂין בּוֹ דְּמוּת שִׁי״ן שֶׁיֵּשׁ לָהּ שְׁלֹשָׁה רָאשִׁין מִיָּמִין הַמֵּנִיחַ תְּפִלִּין וּדְמוּת שִׁי״ן שֶׁיֵּשׁ לָהּ אַרְבָּעָה רָאשִׁים מִשְּׂמֹאל הַמֵּנִיחַ:
כסף משנה
2.
How are the head tefillin made? We take a cubic wooden block.1This appears to be the Rambam's preference. It is not, however, an absolute requirement. [It need not, however, be a perfect cube]. If its height is [slightly] more or less than its width, it is of no consequence. We are required to take care only that its width and length are alike.2Thus, the top of the tefillin must be a perfect square, but its side surfaces need not be square. This ruling is quoted by the Shulchan Aruch and the Ramah (Orach Chayim 32:39).
The Bi'ur Halachah emphasizes that it is not the top surface of the tefillin alone which must be square. At every point along its height, its circumference must be a perfect square. Thus, even if the top surface itself remains square, should the tefillin be crooked or noticeably indented at the sides, they are unacceptable.

Three grooves are carved into it so that four projections will be made as depicted.3The accompanying diagram is based on a drawing by the Rambam himself, which has been copied in all printings of the Mishneh Torah. Leather is taken4Note our commentary on Chapter 2, Halachah 1, regarding making tefillin by sewing or gluing together separate compartments. This halachah indicates the Rambam's preference for tefillin to be made from a single piece of leather. and soaked in water, and then, the mold is placed within it.5The authoritative manuscripts of the Mishneh Torah read, "The leather is placed around the mold." This version more accurately describes the process with which tefillin are actually made. The leather is inserted in between the grooves.6and around theFJ 46sides, so that when it dries four compartments will be created.
While [the leather] is still wet, it is plucked and squeezed7with tweezers. The Orchot Chayim states that one must make the shin in this manner, and it is unacceptable to use a mold. The Beit Yosef (Orach Chayim 32), Shulchan Aruch HaRav 32:65, and the Mishnah Berurah 32:193 all mention that though it is theoretically preferable to follow the Orchot Chayim's ruling, nevertheless, until recently, most shinim were made using a mold. At present, however, there are some manufacturers of tefillin who have reverted to the practice of making the shin with tweezers. until the shape of a shin8The Orchot Chayim mentions that the letter shin is numerically equivalent to 300. In the diaspora, tefillin are worn 300 days during a solar year (according to the opinion which requires that they be worn on chol hamo'ed).
4
with three heads9This is the usual form of the shin. is formed on the right side of the tefillin as they will be worn, and the shape of a shin with four heads10The Beit Yosef (loc. cit.) explains that the letters on the tablets of the Ten Commandments were hewn into the stone. When a three-headed shin is hewn into stone, the protruding stone appears as a four-headedshin. is formed on the left side of the tefillin as they will be worn.11The Ramah (Orach Chayim 32:42) rules that tefillin are not disqualified if the sides on which the two shinim are placed are reversed, so long as they possess both forms of the shin.

הלכה ג
וּמַנִּיחִין אֶת הָעוֹר עַל הָעֵץ עַד שֶׁיִּיבַשׁ. וְאַחַר כָּךְ חוֹלֵץ הָעוֹר מֵעַל גַּבֵּי הָאִמּוּם שֶׁל עֵץ וְנִמְצָא הָעוֹר שֶׁיֵּשׁ בּוֹ אַרְבָּעָה בָּתִּים פְּנוּיִין. וּמַכְנִיסִין פָּרָשָׁה בְּכָל בַּיִת וּבַיִת. וּמַחְזִירִין מִקְצָת הָעוֹר מִלְּמַטָּה וְתוֹפְרִין אוֹתוֹ מֵאַרְבַּע פִּנּוֹתָיו. וּמַנִּיחִין מִן הָעוֹר שֶׁלְּמַטָּה מָקוֹם שֶׁתִּכָּנֵס בּוֹ הָרְצוּעָה כְּמוֹ תּוֹבָר וְהוּא הַנִּקְרָא מַעְבֹּרֶת:
כסף משנה
3.
The leather is then left on the mold until it dries, and then it is removed. Thus, the leather will be [formed into a block] with four empty compartments.1The leather is then left on the mold until it dries, and then it is removed. Thus, the leather will be [formed into a block] with four empty compartments.
One of the passages from the Torah is placed2upright, as a Torah scroll stands in the ark (Shulchan Aruch, Orach Chayim 32:45), with the right side of the passage on the left side of the tefillin (Shulchan Aruch HaRav 32:70). in each compartment,3In Halachah 5, the Rambam describes the order in which the passages are placed into the compartments. and then a portion of the leather is folded over beneath them,4Thus, forming the bottom of the tefillin's base. This is referred to as the titorah, which means "bridge" (Shulchan Aruch, Orach Chayim 32:44). It is given this name because it extends like a bridge below the tefillin (Shulchan Aruch HaRav 32:66). and then they are sewn closed on all four corners.5The precise manner in which the tefillin are sewn closed is described in Halachah 10.
Within this lower piece of leather, a place should be left for the straps to be inserted,6and pass through. This portion should extend outward like a handle.7Alternatively, "loop" (Aruch).
The width of this "handle" should be less than the width of the base of the tefillin, to distinguish it from the base and thus accentuate the base's squareness (Shulchan Aruch HaRav, loc. cit., Mishnah Berurah 32:177).
It is called a ma'aboret.8which literally means "passageway."

הלכה ד
וְכֵיצַד עוֹשִׂין תְּפִלִּין שֶׁל יָד. לוֹקְחִין עֵץ מְרֻבָּע אָרְכּוֹ כְּרָחְבּוֹ וְיִהְיֶה גָּבְהוֹ כְּאֶצְבַּע אוֹ יָתֵר עַל זֶה מְעַט אוֹ פָּחוֹת מְעַט וּמְחַפִּין אוֹתוֹ בְּעוֹר רָטֹב וּמַנִּיחִין אֶת הָעוֹר עַל הָאִמּוּם עַד שֶׁיִּיבַשׁ וְחוֹלֵץ אֶת הָעוֹר וּמַנִּיחַ אֶת אַרְבַּע הַפָּרָשִׁיּוֹת בִּמְקוֹם הָעֵץ וּמַחֲזִיר מִקְצָת הָעוֹר מִלְּמַטָּה וְתוֹפְרוֹ מֵאַרְבַּע פִּנּוֹתָיו. וּמַנִּיחִין מִן הָעוֹר תּוֹבָר מְקוֹם הָרְצוּעוֹת:
כסף משנה
4.
How are the tefillin of the arm made? We take a wooden block whose length is equal to its width1Here, also, a square shape is required at the top of the tefillin, along its entire height, and at its base. and is a fingerbreadth2According to the Shiurei Torah, a fingerbreadth is 2 centimeters in modern measure. The Chazon Ish differs, and considers it 2.4 centimeters. - or slightly more or slightly less3high - Curiously, though the Rambam mentions the preferred size for the arm tefillin in this halachah, he did not suggest a size for the head tefillin in the previous two halachot. Shulchan Aruch HaRav 32:62 relates that people of stature should wear head tefillin that are at least three fingerbreadths high.
Shulchan Aruch HaRav 32:63 and the Mishnah Berurah 32:189 mention that the width and length of the base of the tefillin should be more than one fingerbreadth. Preferably, the width and length of the head tefillin should be two fingerbreadths.
- high, and place wet leather around it.4Thus, forming a single compartment.
The leather is left on this mold until it has dried, and then it is removed. The four passages5which are written on a single piece of parchment are deposited in the place left by the mold.6As mentioned in the previous halachah, the parchment should be placed upright in the compartment. A portion of the leather is folded over beneath them, and then they are sewn closed on all four corners.7See Halachah 10. A piece of leather, like a handle, should be left for the straps [to be inserted].8The ma'aboret of the arm tefillin is governed by the same principles as explained above with regard to the head tefillin.

הלכה ה
כֵּיצַד סִדּוּר הַפָּרָשִׁיּוֹת בִּתְפִלָּה שֶׁל רֹאשׁ. מַכְנִיס פָּרָשָׁה אַחֲרוֹנָה שֶׁהִיא (דברים יא יג) ״וְהָיָה אִם שָׁמֹעַ״ בְּבַיִת רִאשׁוֹן שֶׁהוּא עַל יְמִין הַמֵּנִיחַ. וּ (דברים ו ד) ״שְׁמַע״ סְמוּכָה לָהּ. (שמות יג יא) ״וְהָיָה כִי יְבִיאֲךָ״ בְּבַיִת שְׁלִישִׁי סְמוּכָה לִשְׁמַע. וְ(שמות יג ב) ״קַדֶּשׁ לִי״ בְּבַיִת רְבִיעִי שֶׁהוּא לִשְׂמֹאל הַמֵּנִיחַ תְּפִלִּין כְּדֵי שֶׁיְּהֵא הַקּוֹרֵא שֶׁלְּפָנָיו כְּנֶגֶד פְּנֵי הַמֵּנִיחַ קוֹרֵא עַל הַסֵּדֶר הַזֶּה כְּגוֹן זֶה: וְאִם הֶחֱלִיף סִדּוּר זֶה פְּסוּלוֹת:
כסף משנה
5.
What is the order of the passages? For the head tefillah, the final passage, V'hayah im shamo'a,1The order of the passages chosen by the Rambam - when read by a person facing the person wearing the tefillin - reflects their order in the Torah (Menachot 34b). Hence, V'hayah im shamo'a is referred to as the final passage. is placed in the first compartment on the right side of the person putting on the tefillin. Shema is placed next to it. V'hayah ki y'viacha is placed in the third compartment next to Shema, and Kadesh Li is placed in the fourth compartment, on the left side of the person putting on the tefillin.2Rashi also prescribes this order for the passages of the tefillin, and this is the order that is accepted as halachah (Shulchan Aruch, Orach Chayim 34:1). Many other Torah authorities (among them Rav Hai Gaon and Rabbenu Tam) suggest a different order, placing the two passages that begin V'hayah, V'hayah ki y'viacha and V'hayah im shamo'a in the center, Shema on the right side of the person wearing the tefillin, and Kadesh Li on his left side.
Thus, a person who is facing the person wearing the tefillin will read them in the following order.3The diagram accompanying this halachah is based on a diagram drawn by the Rambam himself and included in all texts of the Mishneh Torah.
Thus, the Rambam (and similarly, Rabbenu Tam and those who follow his opinion) considered that the order of the passages be calculated from the perspective of a person standing opposite the person wearing the tefillin. In contrast, there are other opinions (Shimusha Rabbah and the Ra'avad) who maintain that the order of the passages should be calculated from the perspective of the person wearing the tefillin. (This produces two further perspectives regarding the order of the tefillin. The Shimusha Rabbah follows the same order as the Rambam except that V'hoyoh im Shamoa, is placed in the first compartment on the left side of the person putting on the tefillin, not on the right side. Similarly, the Ra'avad shares Rabbenu Tam's view, but reverses the sides.)
If their order is altered, they are not acceptable.4For this reason, the Shulchan Aruch (Orach Chayim 34:2) suggest that a God-fearing person put on both a pair of tefillin that follow the opinion of the Rambam and Rashi, and a second pair, that follow the opinion of Rabbenu Tam. Though the Shulchan Aruch mentions certain reservations in this regard, in many communities it has become widespread practice to wear both pairs of tefillin.
Significantly, the She'elot UTeshuvot Min HaShamayim writes that with regard to this dispute an answer was received from heaven, "Just as there is a dispute in the earthly realm, there is a dispute in the spiritual realms."

הלכה ו
תְּפִלָּה שֶׁל יָד כּוֹתְבָם בְּאַרְבָּעָה דַּפִּין בְּעוֹר אֶחָד אָרֹךְ כְּסֵפֶר תּוֹרָה עַל סִדּוּרָן בַּתּוֹרָה כְּגוֹן זֶה

אִם כְּתָבָן עַל אַרְבַּע עוֹרוֹת וְהִכְנִיסָן בְּבַיִת אֶחָד יָצָא וְאֵינוֹ צָרִיךְ לְדַבְּקָם:
כסף משנה
6.
[The passages for] the arm tefillin are written on four columns1each passage being written on a separate column on a single piece of parchment2Though this is not an absolute requirement, it is preferable (Shulchan Aruch HaRav 32:72; Mishnah Berurah 32:219). like a Torah scroll,3i.e., the parchment is rolled closed. according to the order in which these passages are found in the Torah,4If the passages, in part or in totality, are not written in order, they are unacceptable and may not be corrected. in the following manner:
If5The diagram accompanying this halachah is based on a diagram drawn by the Rambam himself and included in all texts of the Mishneh Torah. they were written on four separate pieces of parchment and placed in the same compartment, one fulfills one's obligation. There is no need to glue them together.6Although the Ramah (Orach Chayim 32:47) accepts the Rambam's decision, he states that it is customary to glue the parchments together. He emphasizes that it is desirable to use glue that does not contain any non-kosher ingredients.

הלכה ז
כְּשֶׁהוּא גּוֹלֵל הַפָּרָשִׁיּוֹת בֵּין שֶׁל רֹאשׁ בֵּין שֶׁל יָד גּוֹלֵל אוֹתָן מִסּוֹפָן לִתְחִלָּתָן עַד שֶׁתִּמְצָא כְּשֶׁתִּפְתַּח הַפָּרָשָׁה תִּקְרָא כָּל פָּרָשָׁה וּפָרָשָׁה מִתְּחִלָּתָהּ עַד סוֹפָהּ:
כסף משנה
7.
When the passages1both of the head and the arm tefillin - are rolled closed - to be inserted into their compartments. - both of the head and the arm tefillin - are rolled closed, they should be rolled from the end to the beginning,2as a mezuzah must be rolled from אחדtowards שמע(Menachot 31b). so that were the passage to be rolled open, it would be possible to read each portion from the beginning to the end.3The Bi'ur Halachah (32) states that although rolling the passages is preferable, if the parchments were placed in the tefillin without being rolled closed they are acceptable.

הלכה ח
וּכְשֶׁמַּכְנִיסִין אֶת הַפָּרָשִׁיּוֹת בַּבָּתִּים שֶׁלָּהֶם כּוֹרְכִין אוֹתָן בְּמַטְלִית וְעַל הַמַּטְלִית שֵׂעָר וְאַחַר כָּךְ מַכְנִיסִין אוֹתָן בְּבָתֵּיהֶן. וְשֵׂעָר זֶה צָרִיךְ לִהְיוֹת שְׂעַר בְּהֵמָה אוֹ שֶׁל חַיָּה טְהוֹרָה וַאֲפִלּוּ מִנְּבֵלוֹת וּטְרֵפוֹת שֶׁלָּהֶן. וּכְבָר נָהֲגוּ כָּל הָעָם (לְבָרְכָן) [לְכָרְכָן] בִּשְׂעַר זְנַב הָעֲגָלִים:
כסף משנה
8.
Before the passages are placed in their compartments, they should be wrapped in a fabric,1The present custom is to use a piece of parchment (Shulchan Aruch, Orach Chayim 32:44). Although the Rambam considers this requirement to be a halachah transmitted to Moses on Mount Sinai, the Ashkenazic authorities do not agree. Accordingly, they maintain that, after the fact, if the passages are not wrapped in this parchment, the tefillin may still be used (Shulchan Aruch HaRav 32:68; Mishnah Berurah 32:205).
The difference between the Rambam and the Ashkenazic authorities depends on their interpretation of a passage from the Jerusalem Talmud (Megilah, Chapter 1). This difference in interpretation is also reflected in the laws regarding correcting a torn Torah scroll. See Chapter 9, Halachah 15.
and hair should be wound around them. Afterwards, they may be placed in their compartments.2All authorities agree that this is a halachah transmitted to Moses on Mount Sinai.
The difference of opinion of whether it is necessary to wrap the tefillin in parchment has created a difficulty with regard to this obligation. The opinions which do not require that the tefillin be wrapped in parchment require that this hair be wrapped around the passages themselves. In contrast, the Rambam, who maintains that it is necessary to wrap them, obligates the hair to be placed around that wrapping.
In practice, it is customary to satisfy both opinions and wrap the hair around the passages, cover them with a parchment, and then wrap the same hair around the parchment as well (Shulchan Aruch HaRav 32:69, Mishnah Berurah 32:209).

This hair should be from a kosher species of animal or beast.3As explained in Chapter 1, Halachah 10, all the elements required for tefillin must be made from species which may be eaten. Even when these animals died without being ritually slaughtered or were treifah,4wounded or possessing an illness that will cause them to die within a year. The meat of such an animal may not be eaten. [their hair is nevertheless acceptable].5As explained in the commentary on the above-mentioned halachah, although these animals themselves may not be eaten, since they come from a kosher species, they are not disqualified. It has already become a universally accepted custom to wind hair from the tail6The hair from the tail is longer and easier to tie than the hair from the other portions of the body. of a calf7To recall the sin of the Golden Calf (Shimusha Rabbah). [around these parchments].8Based on the Zohar (Parashat Bo), it is customary that the hair which is wound around the passage, V'hayah im shamo'a, be extended and protrude from the compartments slightly (Ramah, Orach Chayim 32:44).

הלכה ט
כְּשֶׁתּוֹפְרִין אֶת הַתְּפִלִּין אֵין תּוֹפְרִין אֶלָּא בְּגִידִין שֶׁל בְּהֵמָה אוֹ שֶׁל חַיָּה טְהוֹרָה וַאֲפִלּוּ מִנְּבֵלוֹת וּטְרֵפוֹת שֶׁלָּהֶן. לוֹקְחִין הַגִּידִין שֶׁיֵּשׁ בַּעֲקֵב הַבְּהֵמָה אוֹ הַחַיָּה טְהוֹרִים וְהֵם לְבָנִים. וְאִם הֵם קָשִׁים מְרַכְּכִין אוֹתָן בַּאֲבָנִים וְכַיּוֹצֵא בָּהֶן עַד שֶׁיֵּעָשׂוּ כְּפִשְׁתָּן וְטוֹוִין אוֹתָן וְשׁוֹזְרִין אוֹתָן וּבָהֶן תּוֹפְרִין הַתְּפִלִּין וִירִיעוֹת סֵפֶר תּוֹרָה:
כסף משנה
9.
When the tefillin are sewn closed, they may be sewn only with sinews1The Shulchan Aruch (Orach Chayim 32:50) states that if sinews are not available, one may sew the tefillin closed with thread made from parchment, until sinews are available. Although there are opinions which object to this ruling, it should be followed if there is no other alternative (Shulchan Aruch HaRav 32:76; Mishnah Berurah 32:227). from a kosher species of animal or beast.2The Shulchan Aruch (Orach Chayim 32:49) states that it is preferable to use the sinews of an ox.
Significantly, the Rambam does not mention sinews from kosher fowl. The Rabbis have not defined which of a fowl's sinews are classified as גידים and which are not. Therefore, it is desirable to use the sinews from beasts or animals, and thus avoid this difficulty (Mishnah Berurah, loc. cit.).
[Sinews taken from] animals which died without being ritually slaughtered or which were treifah [are nevertheless acceptable].3See the previous halachah.
It is customary to take sinews from the heels of kosher animals and beasts. They are white in color. If they are too firm, they are softened by [pounding them with] stones and the like until they become like flax.4This halachah serves as another example of the Rambam's desire for the Mishneh Torah to serve as a complete guide for the fulfillment of the mitzvot. Afterwards, they are spun and twisted into threads5Note Shulchan Aruch HaRav 32:75, which states that the process of spinning the sinews into thread must be carried out with the intent that they be used for this sacred purpose. Accordingly, this process may not be carried out by gentiles. and used to sew together tefillin and the sheets of Torah scrolls.6A Torah scroll contains many sheets of parchment. It is a halachah transmitted to Moses on Mount Sinai to join these sheets by sewing them with sinews, as explained in Chapter 9, Halachah 13.

הלכה י
כְּשֶׁתּוֹפְרִין הַתְּפִלִּין תּוֹפְרִין אוֹתָן בְּרִבּוּעַ. וַהֲלָכָה רוֹוַחַת שֶׁיִּהְיוּ בְּכָל צַד שָׁלֹשׁ תְּפִירוֹת עַד שֶׁיִּהְיוּ הַכּל שְׁתֵּים עֶשְׂרֵה תְּפִירוֹת בֵּין שֶׁל יָד בֵּין שֶׁל רֹאשׁ. וְאִם עָשָׂה הַתְּפִירוֹת עֶשֶׂר אוֹ אַרְבַּע עֶשְׂרֵה עוֹשֶׂה. וְכָל הַתְּפִירוֹת יִהְיֶה הַחוּט שֶׁלָּהֶן סוֹבֵב מִשְּׁתֵּי רוּחוֹת:
כסף משנה
10.
When the tefillin are sewn closed,1If the base of the tefillin is made from a separate piece of leather from the compartments, the stitches must also be connected to the edges of the skin covering the compartments (Shulchan Aruch HaRav 32:77; Mishnah Berurah 32:228). they should be sewn as a square.2If the stitches are sewn in any other shape, the tefillin are unacceptable. It is a widely accepted practice for there to be three stitches on each side, so that there will be twelve stitches in all.3The Shimusha Rabbah interprets this to be an allusion to the twelve tribes of Israel. This applies for both the arm tefillin and the head tefillin. If, however, one made ten or fourteen stitches, there is no difficulty.4Although the simple meaning of the Rambam's statements is that any number of stitches is acceptable, the commentaries have noted that the Shimusha Rabbah also attaches significance to the numbers ten and fourteen. Ten represents the twelve tribes minus Levi (the priestly tribe) and Judah (the tribe of royalty). Fourteen includes also the tribes of Menasheh and Ephraim.
For each of the stitches, the thread5or threads must pass through from both sides.6The tefillin should be sewn closed with two needles: one which is initially passed through facing the upper side of the tefillin, and one which is initially facing their lower side (Mishnah Berurah 32:230).

הלכה יא
וְצָרִיךְ שֶׁיַּגִּיעַ הֶחָרִיץ שֶׁל תְּפִלִּין שֶׁל רֹאשׁ עַד מְקוֹם הַתֶּפֶר. וְאִם הָיָה הֶחָרִיץ נִכָּר כְּדֵי שֶׁיִּהְיוּ אַרְבָּעָה רָאשִׁין נִרְאִין לַכּל וְאַף עַל פִּי שֶׁאֵין הֶחָרִיץ מַגִּיעַ לִמְקוֹם הַתֶּפֶר כְּשֵׁרוֹת. וְאִם אֵין חָרִיץ נִכָּר פְּסוּלוֹת. וְצָרִיךְ לְהַעֲבִיר בְּתוֹךְ כָּל חָרִיץ וְחָרִיץ עַל גַּבֵּי הָעוֹר חוּט אוֹ מְשִׁיחָה לְהַבְדִּיל בֵּין בַּיִת לְבַיִת. וּמִנְהָג פָּשׁוּט לְהַעֲבִיר גִּיד מִגִּידֵי הַתְּפִירָה בְּכָל חָרִיץ וְחָרִיץ מִשְּׁלָשְׁתָּן:
כסף משנה
11.
The groove between [each of the compartments] of the head tefillin should reach the stitches [which sew the tefillin closed].1Thus, the separation between the compartments will be both external and internal. [Nevertheless,] if the groove is discernible, so that the [division into] four compartments is openly visible, [the tefillin] are acceptable even if the groove does not extend until the stitches.2i.e., the separation between the compartments does not extend through the total height of the tefillin. If, however, the groove is not discernible, [the tefillin] are not acceptable.3Note the Mishnah Berurah 32:187, which states that if the groove between the tefillin is not discernible, the tefillin are not acceptable even if they are divided into four separate compartments. Needless to say, however, if only an external distinction is made, but inside, there is no separation between the compartments, the tefillin are not acceptable (Shulchan Aruch HaRav 32:61).
It is necessary to pass a thread or cord through each of the grooves on [the outer side of] the leather [compartments] to separate between the compartments.4This decision is not accepted by all the authorities. Tosafot, Menachot 32b, states that it is necessary to pass a cord between the compartments only when all four passages are written on a single piece of parchment. See Shulchan Aruch HaRav 32:71, Mishnah Berurah 32:217. It is common custom to pass one of the sinews used to sew [the tefillin closed] between each of these three grooves.5This halachah raises questions with regard to the process in which tefillin are customarily made today. At present, after the compartments of the tefillin are fashioned into a single block, a sinew is passed between the compartments. Afterwards, they are glued together, and then the entire block is shaped into a square. The grooves we see do not represent the real divisions between the blocks, but are merely external impressions.
This process is employed, because were the compartments not to be glued together, it would be difficult to form the tefillin into a square. Even if that were possible at the outset, problems might arise over the course of time, because the compartments might spread further apart, and thus prevent the square shape from being maintained. Though it is acceptable to use tefillin made in the present manner, the Rabbis suggest using those in which the separation between the compartments remains openly visible afterwards. (See the Responsa of the Chatam Sofer, Orach Chayim 5; and the Bi'ur Halachah 32.)

הלכה יב
וְכֵיצַד עוֹשִׂין הָרְצוּעוֹת. לוֹקְחִין רְצוּעָה שֶׁל עוֹר רְחָבָה כְּאֹרֶךְ הַשְּׂעוֹרָה. וְאִם הָיְתָה רְחָבָה מִזּוֹ הַשִּׁעוּר כְּשֵׁרָה. וְאֹרֶךְ רְצוּעָה שֶׁל רֹאשׁ כְּדֵי שֶׁתַּקִּיף אֶת הָרֹאשׁ וְיִקְשֹׁר מִמֶּנָּה הַקֶּשֶׁר וְתִמְתַּח שְׁתֵּי הָרְצוּעוֹת מִכָּאן וּמִכָּאן עַד שֶׁיַּגִּיעוּ לַטַּבּוּר אוֹ לְמַעְלָה מִמֶּנּוּ מְעַט. וְאֹרֶךְ רְצוּעָה שֶׁל יָד כְּדֵי שֶׁתַּקִּיף אֶת הַזְּרוֹעַ וְיִקְשֹׁר מִמֶּנָּה הַקֶּשֶׁר וְתִמָּתַח רְצוּעָה אַחַת עַל אֶצְבַּע אֶמְצָעִית וְיִכְרֹךְ מִמֶּנָּה עַל אֶצְבָּעוֹ שָׁלֹשׁ כְּרִיכוֹת וְיִקְשֹׁר. וְאִם הָיוּ הָרְצוּעוֹת אֲרֻכּוֹת יָתֵר עַל שִׁעוּרִים הָאֵלּוּ כְּשֵׁרוֹת:
כסף משנה
12.
How are the straps made? We take leather straps1See Halachah 15. [at least] the length of a barley-corn in width.2The Mishnah Berurah 27:42 emphasizes that when the tefillin are being tied around the arm, care must be taken that the straps do not wrinkle - particularly around the knot, where it is natural that they do - so that this minimum width is maintained.
Based on Chapter 9, Halachah 9, we can conclude that this measure is approximately 1 centimeter according to Shiurei Torah and 1.2 centimeters according to Chazon Ish.
If they are wider than that, they are acceptable. The length of the straps of the head tefillin should be sufficient to surround the head, tie the knot,3See the following halachah. and extend on either side of the head until they reach the navel or slightly above it.4The Tur (Orach Chayim 27) writes that, according to one opinion, the strap on the right side should reach the navel and the strap on the left should reach the chest. Another opinion states that the right strap should reach the genitalia, and the left, the navel.
The length of the strap of the arm should be sufficient to surround the forearm,5at the muscle (Chapter 4, Halachah 2) tie its knot,6See the following halachah. and extend7Significantly, neither in this halachah nor in the following chapter, where the Rambam describes the manner in which tefillin are worn, does he mention the custom of winding the tefillin strap seven times around the arm. until it can be wound three times around the middle finger and tied.8In one of his responsa, the Rambam explains that although the verse, "And you shall tie them for a sign on your hand," refers to the knot tied on the forearm, our Sages divided the word וקשרתם in half, תם וקשר, meaning "And you shall tie a perfect knot." For the knot of the tefillin to be "perfect," the straps should be tied on the hand as well. If the straps are longer than this, they are acceptable.9From the Rambam's statements in Halachah 19, it would appear that he maintains that the minimum standards mentioned in this halachah are absolute requirements.
The Shulchan Aruch (Orach Chayim 27:11) states that since the minimum measure mentioned in this halachah for the head tefillin is not found in the Talmud, if the only tefillin available do not have straps that conform to these measures, these tefillin should be worn. The straps of the head tefillin, however, must be long enough so that they can be draped in front of the person at least slightly (Shulchan Aruch HaRav 27:22; Mishnah Berurah 27:44).

הלכה יג
וּמַכְנִיס רְצוּעָה שֶׁל רֹאשׁ בַּתּוֹבָר שֶׁלָּהּ. וּמַקִּיף בְּמִדַּת רֹאשׁוֹ וְקוֹשֵׁר קֶשֶׁר מְרֻבָּע כְּמִין דָּלֶ״ת. וְקֶשֶׁר זֶה צָרִיךְ כָּל תַּלְמִיד חָכָם לְלָמְדוֹ וְאִי אֶפְשָׁר לְהוֹדִיעַ צוּרָתוֹ בִּכְתָב אֶלָּא בִּרְאִיַּת הָעַיִן. וְכֵן בְּשֶׁל יָד קוֹשֵׁר קֶשֶׁר כְּמִין יוּ״ד. וְתִהְיֶה הָרְצוּעָה שֶׁל יָד עוֹלָה וְיוֹרֶדֶת בְּתוֹךְ הַקֶּשֶׁר כְּדֵי שֶׁיַּרְחִיב וִיקַצֵּר בְּעֵת שֶׁיִּרְצֶה לִקְשֹׁר עַל יָדוֹ:
כסף משנה
13.
One places the straps through their handle,1The extension of the tefillin's base described in Halachah 4. leaving space for the [circumference of] one's head, and ties2The Pri Megadim writes that this knot must be tied with the specific intent that it be used for the mitzvah. a square knot, which resembles a dalet.3The Rambam's intent is that though the knot is square, the straps extending from either side each appearFJ 46as the legs of a dalet. Note the Beit Yosef (Orach Chayim 32), which states that it is preferable to tie a knot which is shaped like a dalet itself. (Unlike the Rambam's knot, which is square, this knot is a right angle.) Sephardic and Chassidic custom is to follow the Beit Yosef. Ashkenazim and Yemenites follow the Rambam's view. Every Torah scholar should learn how to tie this knot.4Chulin 9a mentions this as one of the basic points of knowledge which every Torah scholar should possess. It is impossible to describe this knot in writing. Rather, it must be seen.5The Eshkol associates this statement with the interpretation (Menachot 35b) of Exodus 33:23: "And you shall see My rear," that God showed Moses the knot of His head tefillin. Since it is impossible to describe that knot, God actually showed it to Moses.
The straps of the hand tefillin should be tied with a knot that resembles a yud.6The Tur (Orach Chayim 32) writes that - together with the shin embossed on the head tefillin and the dalet mentioned above - this yud completes God's name ידש.
Significantly, in Halachah 1, the Rambam does not mention the yud as a "halachah transmitted to Moses on Mount Sinai." Our text of Shabbat 62a confers that status on all three of these letters. Tosafot (Shabbat, loc. cit.) suggests emending the text of that passage and conferring that status on the shin alone.The Rambam appears to take an intermediate position.
This knot should7have a loop to allow the strap to pass through it so that it can be widened or narrowed while one is tying the tefillin on one's arm.

הלכה יד
הָרְצוּעוֹת שֶׁל תְּפִלִּין בֵּין שֶׁל רֹאשׁ בֵּין שֶׁל יָד פְּנֵיהֶם הַחִיצוֹנִים שְׁחוֹרִים וְזוֹ הֲלָכָה לְמשֶׁה מִסִּינַי. אֲבָל אֲחוֹרֵי הָרְצוּעוֹת הוֹאִיל וּמִבִּפְנִים הֵן אִם הָיוּ יְרֻקּוֹת אוֹ לְבָנוֹת כְּשֵׁרוֹת. אֲדֻמּוֹת לֹא יַעֲשֶׂה שֶׁמָּא תֵּהָפֵךְ הָרְצוּעָה וּגְנַאי הוּא לוֹ. וְלֹא יִהְיֶה אֲחוֹרֵי הָרְצוּעָה לְעוֹלָם אֶלָּא כְּעֵין הַקְּצִיצָה אִם יְרֻקָּה יְרֻקִּין וְאִם לְבָנָה לְבָנִים. וְנוֹי הוּא לַתְּפִלִּין שֶׁיִּהְיוּ כֻּלָּן שְׁחוֹרוֹת הַקְּצִיצָה וְהָרְצוּעָה כֻּלָּהּ:
כסף משנה
14.
The outer surface of the straps of both the head and the arm tefillin must be black.1The Shulchan Aruch (Orach Chayim 33:4) states that it is preferable that the straps be dyed black by a Jew with the intent that they be used for the mitzvah of tefillin. According to the Ramah, this is an absolute requirement. This is a halachah transmitted to Moses on Mount Sinai.2The straps must remain black at all times. Frequently, after the tefillin have been worn for an extended period, the dye on the straps begins to fade (in particular, near the knots). Since the color of the straps is "a halachah transmitted to Moses on Mount Sinai," the tefillin are unacceptable if that color has faded. Accordingly, from time to time, it is desirable to check the straps and, if necessary, dye them again (Mishnah Berurah 33:19).
In contrast, with regard to the inner surface, since it faces the inside, it is acceptable if it is green or white.3or any other color (Shulchan Aruch, Orach Chayim 33:3). One should not make this [side of the straps] red, since it will be embarrassing for him if they become overturned.4People might think that he is infested with skin ulcers and it is the blood oozing from them which makes the straps red (Rashi, Menachot 35a).
The back of the straps should be the same color as the compartment;5before it is dyed; alternatively, the color of the underside of the compartment (Kin'at Eliyahu). if it is green, they should be green; if it is white, they should be white.6i.e., it should be the natural color of the leather. It is attractive for tefillin to be entirely black, the compartments7The Shulchan Aruch (Orach Chayim 32:40) uses the expression, "It is a mitzvah that they be black." The Nodah B'Yehudah (Orach Chayim 1) cites the Jerusalem Talmud (Megillah 1:9), which states that it is a halachah transmitted to Moses on Mount Sinai that the compartments be black. The Rambam, however, does not consider dyeing the compartments an obligation of this nature. and the entire strap.8i.e., both sides. This practice was never widely accepted (Beit Yosef, Orach Chayim 33).

הלכה טו
הָעוֹר שֶׁמְּחַפִּין בּוֹ הַתְּפִלִּין וְשֶׁעוֹשִׂין מִמֶּנּוּ הָרְצוּעוֹת הוּא עוֹר שֶׁל בְּהֵמָה אוֹ חַיָּה אוֹ עוֹף הַטְּהוֹרִים וַאֲפִלּוּ נְבֵלוֹת וּטְרֵפוֹת שֶׁלָּהֶן. וְאִם עָשָׂה מֵעוֹר טְמֵאִים אוֹ שֶׁחִפָּה תְּפִלִּין בְּזָהָב פְּסוּלוֹת. וְעוֹר הָרְצוּעָה צָרִיךְ עִבּוּד לִשְׁמָהּ. אֲבָל בְּעוֹר שֶׁמְּחַפִּין בּוֹ אֵינוֹ צָרִיךְ עִבּוּד כְּלָל אֲפִלּוּ עֲשָׂהוּ מַצָּה כָּשֵׁר. וּמְקוֹמוֹת הַרְבֵּה נָהֲגוּ לַעֲשׂוֹת אוֹתָן בְּעוֹר מַצָּה:
כסף משנה
15.
The leather used to cover the tefillin1i.e., the compartments and from which the straps are made should come from a kosher species of animal, beast, or fowl. Even when these animals died without being ritually slaughtered or were treifah, [their hides are nevertheless acceptable].2Shabbat 108a derives this concept through the exegesis of Exodus 13:9, "So that the Torah of God will be in your mouths." If, however, leather from a non-kosher species3since it is not permitted to be eaten, it may not be used for tefillin was used or if they were covered with gold, they are not acceptable.4The Rambam appears to be stating that the compartments themselves may not be made from leather from a non-kosher species or from gold. The Shulchan Aruch (Orach Chayim 32:48), adds that this prohibition forbids attaching these substances to kosher tefillin.
The leather used for the straps must be processed with the intent that it be used for the mitzvah.5If it was not processed with this intent, it is unacceptable (Shulchan Aruch HaRav 33:3; Mishnah Berurah 33:17). In contrast, the leather used to cover the tefillin6i.e., the compartments need not be processed at all.7Accordingly, if processed, it is not necessary that it be processed with the intent that it be used for a mitzvah.
The Rambam's view is not accepted by most authorities. Rabbenu Asher states that the leather must be processed and that the processing must be carried out with the intent that the leather be used for the mitzvah. The Shulchan Aruch (Orach Chayim 32:37) accepts Rabbenu Asher's view, but writes that if no other tefillin are available, it is possible to rely on the Rambam's opinion.
It is even acceptable if it is made from matzah.8Shabbat 79a describes this as leather which was not processed with flour and salt and, therefore, likened to matzah, which is simple, without any flavoring. [Indeed,] this is the practice in many communities.9In one of his responsa, the Rambam writes that such leather is used because it is easier to shape. Others state that such leather becomes firmer.

הלכה טז
אֵין עוֹשִׂין הַתְּפִלִּין אֶלָּא יִשְׂרָאֵל שֶׁעֲשִׂיָּתָן כִּכְתִיבָתָן מִפְּנֵי הַשִּׁי״ן שֶׁעוֹשִׂין בָּעוֹר כְּמוֹ שֶׁאָמַרְנוּ. לְפִיכָךְ אִם חִפָּן הַכּוּתִי אוֹ תְּפָרָן פְּסוּלוֹת וְהוּא הַדִּין לְכָל הַפָּסוּל לְכָתְבָן שֶׁלֹּא יַעֲשֶׂה אוֹתָן:
כסף משנה
16.
tefillin may be made only by a Jew, since making them is equivalent to writing [the passages],1for which a gentile is disqualified, as explained in Chapter 1, Halachah 13. because of the shin [embossed] in the leather [compartment] mentioned above.2Halachah 2. Since embossing that shin is equivalent to writing, it must be done by a Jew with the proper intent. Therefore, if they were made by a gentile or sewn closed by him, they are unacceptable.3The Beit Yosef (Orach Chayim 39) explains that since making tefillin has one element which is equivalent to writing the passages, every deed connected with making them may be performed only by those permitted to write them.
Similarly, they may not be made by any others whose writing [of the passages] is not acceptable.4for example, an apostate, a woman, a minor, or a Canaanite slave (Chapter 1, Halachah 13).

הלכה יז
תְּפִלָּה שֶׁל רֹאשׁ אֵין עוֹשִׂין אוֹתָהּ שֶׁל יָד וְשֶׁל יָד עוֹשִׂין אוֹתָהּ שֶׁל רֹאשׁ לְפִי שֶׁאֵין מוֹרִידִין מִקְּדֻשָּׁה חֲמוּרָה לִקְדֻשָּׁה קַלָּה. וְכֵן רְצוּעָה שֶׁל תְּפִלָּה שֶׁל רֹאשׁ אֵין עוֹשִׂין אוֹתָהּ לִתְפִלָּה שֶׁל יָד. בַּמֶּה דְּבָרִים אֲמוּרִים כְּשֶׁלְּבָשָׁן. אֲבָל תְּפִלִּין שֶׁל רֹאשׁ שֶׁלֹּא לְבָשָׁן אָדָם מֵעוֹלָם אִם רָצָה לְהַחֲזִירָן לְיָד מֻתָּר. וְכֵיצַד עוֹשִׂין. טוֹלֶה עָלֶיהָ עוֹר עַד שֶׁתֵּעָשֶׂה אַחַת וְקוֹשְׁרָהּ עַל יָדוֹ:
כסף משנה
17.
A head tefillah may not be made into an arm tefillah,1for the reason to be explained immediately but an arm tefillah may be made into a head tefillah,2by making four compartments, separating the passages, and placing each one in its respective compartment. Similarly, a shin must be embossed on either side of the tefillin. because an article should not be lowered from a higher level of holiness3Rashi (Menachot 34b) explains that the head tefillin are considered to be on a higher level because they have the first two letters of the name שדי (the embossed shin and the dalet of the knot). In contrast, the arm tefillah has only one letter, the yud of the knot. to a lesser one.4This principle is applied in many other contexts in Torah law. For example, Hilchot tefillah 11:14 states that a house of study may not be transformed into a synagogue, because a house of study is on a higher level of holiness. Similarly, the strap of a head tefillah should not be used for an arm tefillah.5Within its discussion of these laws, the Shulchan Aruch (Orach Chayim 42:3) also mentions the prohibition against using articles associated with tefillin - e.g., a carrying bag - for mundane purposes.
When does the above apply? After one has worn them. However, if head tefillin have never been worn, one may make them into arm tefillin.6The commentaries explain that this halachah communicates a fundamental principle of Torah law, הזמנה, designating an article to be used for a sacred purpose, alone is not sufficient for this holiness to be imparted to them. They must first be used for the purpose for which they were intended.
[Homiletically, this teaches us how important it is to express in deed all the resolves which we have made.]
How is this done? One drapes leather around them until they become a single [compartment] and [then, one can] tie them on his hand.7The fact that inside, they are still divided into four compartments is not significant.

הלכה יח
תְּפִלִּין שֶׁנִּפְסְקוּ הַתְּפִירוֹת שֶׁלָּהֶן אִם הָיוּ שְׁתֵּי הַתְּפִירוֹת זוֹ בְּצַד זוֹ אוֹ שֶׁנִּפְסְקוּ שָׁלֹשׁ תְּפִירוֹת אֲפִלּוּ זוֹ שֶׁלֹּא כְּנֶגֶד זוֹ הֲרֵי אֵלּוּ פְּסוּלוֹת. בַּמֶּה דְּבָרִים אֲמוּרִים בִּישָׁנוֹת אֲבָל בַּחֲדָשׁוֹת כָּל זְמַן שֶׁפְּנֵי טַבְלָן קַיָּמוֹת כְּשֵׁרוֹת. וְאֵלּוּ הֵן הַחֲדָשׁוֹת כָּל שֶׁאוֹחֲזִין מִקְצָת הָעוֹר שֶׁנִּקְרַע תִּפְרוֹ וְתוֹלִין בּוֹ הַתְּפִלִּין וְהוּא חָזָק וְאֵינוֹ נִכְרָת הֲרֵי אֵלּוּ חֲדָשׁוֹת. וְאִם אֵין רָאוּי לִתְלוֹת בּוֹ אֶלָּא הוּא נִפְסָק הֲרֵי אֵלּוּ יְשָׁנוֹת:
כסף משנה
18.
[The following laws apply when] the stitches of the tefillin1which sew the upper portion of the tefillin's base to the lower portion, as described in Halachot 9 and 10 become torn: If two stitches which are located next to each other become torn, or three stitches become torn even though they are not located next to each other, [the tefillin] are unacceptable.2Menachot 35a mentions these laws with regard to "tefillin being torn." The Rambam explains that this refers to the stitches, as stated in this halachah. Rabbenu Asher, however, interprets this passage as referring to the leather separating one of the compartments of the head tefillin from the other. The Shulchan Aruch (Orach Chayim 33:1-2) quotes both opinions as halachah.
When does the above apply? With regard to old [tefillin]. With regard to new [tefillin], however, if their base remains intact, they are acceptable.3Our translation of טבלה as "base" follows the interpretation of most authorities. Note, however, the Bi'ur Halachah (33), which stresses the emphasis the Rambam placed on the stitches being sewn in a square shape. (See Halachot 1 and 10.) If some of the stitches are torn, he explains, then the shape of these stitches may no longer be square, and that is the difficulty to which the Rambam is referring. Thus, he interprets טבלה is referring to "the square shape of the stitches." [tefillin are considered] to be "new" as long as the leather remains strong and does not tear when one takes hold of a portion of the leather where the stitch was torn and hangs the tefillin. If the leather is not fit to hang the tefillin because it will tear, the [tefillin are considered] "old."4Note that Rashi (Menachot, loc. cit.) and others interpret the passage as ruling more leniently with regard to "old" tefillin than "new" tefillin. Accordingly, Shulchan Aruch HaRav 33:2 and the Mishnah Berurah 33:15 state that, at the outset, one should follow the stringencies implied by both opinions, and replace the stitches whether the tefillin are new or old. If that is impossible and it is impossible for the person to obtain other tefillin, he may wear those with torn stitches whether they are new or old.

הלכה יט
רְצוּעָה שֶׁנִּפְסְקָה אֵין קוֹשְׁרִין אוֹתָהּ וְאֵין תּוֹפְרִין אוֹתָהּ אֶלָּא מוֹצִיאָהּ וְגוֹנְזָהּ וְעוֹשִׂין אַחֶרֶת. וְשִׁיּוּרֵי הָרְצוּעָה פְּסוּלִין עַד שֶׁיְּהֵא אָרְכָּהּ וְרָחְבָּהּ כַּשִּׁעוּר אוֹ יָתֵר עָלָיו. וּלְעוֹלָם יִזָּהֵר לִהְיוֹת פְּנֵי הָרְצוּעָה לְמַעְלָה בְּעֵת שֶׁקּוֹשֵׁר אוֹתָן עַל יָדוֹ וְעַל רֹאשׁוֹ:
כסף משנה
19.
Should a strap be torn, [the pieces] should not be tied or sewn together.1Menachot 35b derives this concept from the word וקשרתם, “And you shall tie them." As mentioned, this word can be divided in half – תם וקשר - which means "and you shall tie perfectly." Rather, it should be removed and entombed,2Since it was used for a mitzvah, it may not be discarded casually (Megillah 26b). and another one [substituted for it].3The Shulchan Aruch (Orach Chayim 33:5) mentions an opinion which allows one to sew (but not tie) the two portions of the torn strap together. It concludes that it is preferable to follow the Rambam's view, but if there is no alternative, the more lenient opinion may be followed.
The remnants of [torn] straps are not acceptable4i.e., if a strap tears, one may not continue using one of the pieces unless their length and width meets5or exceeds - the minimum requirements - mentioned in Halachah 12. - or exceeds - the minimum requirements.
At all times, a person should be careful that the external surface of the straps faces upward6Menachot 35b states, "Their attractive side should face outward." Mo'ed Katan 25a relates that Rav Huna fasted for forty days to atone for the fact that his tefillin strap once became overturned. when he ties them on his arm and head.7Shulchan Aruch HaRav 27:19 and the Mishnah Berurah 27:38 place greater emphasis on the portion of the strap which is tied around one's head and arm. If these portions of the strap become overturned, one should seek atonement by fasting or by donating to charity. Nevertheless, care should also be taken that the remainder of the straps do not turn over.

אהבה הלכות תפילין ומזוזה וספר תורה פרק ג
Ahavah Tefillin, Mezuzah, and Sefer Torah Chapter 3