עבודה
הלכות בית הבחירה
פרק ב

Halacha

הלכה א
הַמִּזְבֵחַ מְקוֹמוֹ מְכֻוָּן בְּיוֹתֵר. וְאֵין מְשַׁנִּין אוֹתוֹ מִמְּקוֹמוֹ לְעוֹלָם. שֶׁנֶּאֱמַר (דברי הימים א כב א) "זֶה מִזְבַּח לְעוֹלָה לְיִשְׂרָאֵל". וּבַמִּקְדָּשׁ נֶעֱקַד יִצְחָק אָבִינוּ שֶׁנֶּאֱמַר (בראשית כב ב) "וְלֶךְ לְךָ אֶל אֶרֶץ הַמֹּרִיָּה". וְנֶאֱמַר בְּדִבְרֵי הַיָּמִים (דברי הימים ב ג א) "וַיָּחֶל שְׁלֹמֹה לִבְנוֹת אֶת בֵּית ה' בִּירוּשָׁלַיִם בְּהַר הַמּוֹרִיָּה אֲשֶׁר נִרְאָה לְדָוִיד אָבִיהוּ אֲשֶׁר הֵכִין בִּמְקוֹם דָּוִיד בְּגֹרֶן אָרְנָן הַיְבוּסִי":
כסף משנה
1.
The Altar is [to be constructed] in a very precise location,1As emphasized by the various events mentioned in this and the following halachot.
The location of the Altar within the Temple Courtyard is discussed in Chapter 5, Halachot 12-16.
which may never be changed,2In this context, we can understand the Rambam's choice of words, when describing the achievements of the Mashiach (Hilchot Melachim 11:1): "He will build the Sanctuary in its place." There, he does not state "its precise location," for although the Messianic Temple in its entirety will also be built on Mt. Moriah, certain aspects of it will not correspond exactly to the Temples. Nevertheless, even then, the Altar in particular will be positioned in precisely the same location as before. as it is said (II Chronicles 22:1 : "This is the Altar for the burnt offerings of Israel."
Isaac was prepared as a sacrifice on the Temple's [future] site, as it is said (Genesis 22:2 : "Go to the land of Moriah,"3Pirkei D'Rabbi Eliezer relates that the altar which Abraham constructed on Mt. Moriah had twelve stones. Later, when Jacob journeyed to Charan (Genesis, ch. 28), he slept on Mt. Moriah and "took from the stones of the place and put them at his head." The stones he collected were the twelve used by Abraham. God fused them all into a single stone and the unified rock was embedded in the very foundation of the earth. That stone was referred to as Even HaShtiah, (see also Chapter 4, Halachah 1) "the foundation stone." It was located in the Holy of Holies.
Thus, Abraham's altar was apparently not built on the site of the altar to be built by his descendants, but rather, at the ultimate location of the Holy of Holies. However, this difficulty can be resolved. Jacob "took from the stones," and moved them from their original place, the Altar's future site, to a different location, that of the Holy of Holies.
and in Chronicles (II 3:1), it is said: "Then, Solomon began to build the House of the Lord in Jerusalem, on Mt. Moriah, where [the Lord] appeared to David, his father, in the place that David had prepared,4Though David was not allowed to build the Temple, he purchased the site, constructed an altar, and offered sacrifices there.
Zevachim 62a relates that David used prophetic vision in choosing the site of the altar. According to one opinion, he saw the Heavenly Altar on which the angel Michael offers sacrifices. According to a second view, he saw the ashes of Isaac.
in the threshing floor of Ornan, the Jebusite."

הלכה ב
וּמָסֹרֶת בְּיַד הַכּל שֶׁהַמָּקוֹם שֶׁבָּנָה בּוֹ דָּוִד וּשְׁלֹמֹה הַמִּזְבֵּחַ בְּגֹרֶן אֲרַוְנָה הוּא הַמָּקוֹם שֶׁבָּנָה בּוֹ אַבְרָהָם הַמִּזְבֵּחַ וְעָקַד עָלָיו יִצְחָק. וְהוּא הַמָּקוֹם שֶׁבָּנָה בּוֹ נֹחַ כְּשֶׁיָּצָא מִן הַתֵּבָה. וְהוּא הַמִּזְבֵּחַ שֶׁהִקְרִיב עָלָיו קַיִן וְהֶבֶל. וּבוֹ הִקְרִיב אָדָם הָרִאשׁוֹן קָרְבָּן כְּשֶׁנִּבְרָא וּמִשָּׁם נִבְרָא. אָמְרוּ חֲכָמִים אָדָם מִמְּקוֹם כַּפָּרָתוֹ נִבְרָא:
כסף משנה
2.
It is universally accepted5The commentaries explain that this phrase refers to the Gentiles. Even they recognized the holiness of the Altar's site.
The fact that the Gentiles were aware that the site of the Altar is holy is Halachically relevant. The pagans living in Eretz Yisrael before its conquest by the Jewish people were so idolatrous that our Sages declared: "Wherever you see a lofty mountain ...or a leafy tree, know that idols were worshipped there." Since the Temple Mount was also a high mountain, surely it would have been considered an appropriate place for pagan rites.
However, since the holiness of the Altar's site was universally accepted, even the Gentiles did not profane its sanctity with idol worship.
that the place on which David and Solomon built the Altar,6David and Solomon did not build the same Altar. Rather, David chose the site as the future location of the Temple, and constructed an Altar and offered sacrifices. Later, when Solomon built the Temple, he erected a new Altar at the same site. the threshing floor of Ornan, is the location where Abraham built the Altar on which he prepared Isaac for sacrifice.
Noah built [an altar] on that location when he left the ark.7See Genesis 8:20. It was also [the place] of the Altar on which Cain and Abel brought sacrifices.8See ibid. 4:3-5. [Similarly,] Adam, the first man, offered a sacrifice there and was created at that very spot,9The Rambam entitled this collection of Halachot, Hilchot Beit HaBechirah, the Laws of God's Chosen House, implying that God did not select Mount Moriah as the Temple site because of its inherent holiness, but because of His own choice and desire. That choice was clearly expressed in the previous Halachah which states: "the place of the Altar is extremely exact... as it is said: 'This is the altar for the burnt offerings of Israel.'
As such, it can be explained that the Rambam does not recount the various historical events mentioned in this Halachah just to bring further proof of the holiness of the Altar's site. That is unnecessary. Rather, he wanted to demonstrate that many righteous men were aware of the uniqueness of the Altar's site through prophetic vision, and for this reason, they made efforts to offer their sacrifices there.
Why does the Rambam relate all these historical events? As he clearly states in his introduction to the Mishneh Torah, his goal is not to summarize the Talmud's teachings regarding a particular subject, but to describe how to carry out the various mitzvot. These historical facts do not seem to facilitate his objective.
The need for these additions may be explained by comparison to the Rambam's decisions regarding the right to the monarchy. In that context, the Rambam writes that although God chose David and his descendants as kings and endowed them with the monarchy forever, there was a Halachic legitimacy to the establishment of the Kingdom of Israel (the ten tribes). Since the first king, Jereboam, was appointed by a prophet, his regal power must be recognized. (Hilchot Melachim 1:7,8).
It could be inferred that a similar ruling might apply in regard to the altar: i.e. the Altar on Mount Moriah would remain holy forever, however, another altar of similar status could also be established. In order to eliminate that presumption, the Rambam presents a number of examples, illustrating that throughout the generations, from the time of Adam, the prophets had tried to bring sacrifices on this site alone. These efforts clearly imply that there is not, nor will there be, another place with a similar degree of holiness (Likkutei Sichot, Vol. 19, p.140-7).
as our Sages said: "Man was created from the place where he [would find] atonement."10This statement is somewhat problematic. Though the Rambam's statements have a basis in the Midrash (Bereishit Rabbah 14:8), according to Sanhedrin 38b, Adam appears to have been created in the Garden of Eden, a considerable distance from this location. Generally, when a conflict arises between sources, the decision is based upon the Babylonian Talmud. Hence, one might ask why the Rambam favored the other sources in this case.

הלכה ג
מִדּוֹת הַמִּזְבֵּחַ מְכֻוָּנוֹת הַרְבֵּה וְצוּרָתוֹ יְדוּעָה אִישׁ מֵאִישׁ. וּמִזְבֵּחַ שֶׁבָּנוּ בְּנֵי הַגּוֹלָה כְּעֵין מִזְבֵּחַ שֶׁעָתִיד לְהִבָּנוֹת עָשׂוּהוּ וְאֵין לְהוֹסִיף עַל מִדָּתוֹ וְלֹא לִגְרֹעַ מִמֶּנָּה:
כסף משנה
3.
The dimensions of the Altar must be very precise. Its design has been passed down from one to another [over the course of the generations].
The altar built by the exiles [returning from Babylon] was constructed according to the design of the Altar to be built in the Messianic age.11Its dimensions differed from the altar built by King Solomon in the First Temple. As mentioned in Chapter 1, Halachah 4, the fundamental design of the Second Temple resembled that of Solomon's Temple. However, certain aspects were altered to conform with Ezekiel's vision of the Messianic Temple. The dimensions and design of the altar are mentioned in Ezekiel 43:13-17 and were followed by the exiles when they returned to Jerusalem. We may not increase or reduce its dimensions.12As explained in Halachah 17, the Altar is acceptable even if its dimensions are not exact. Nevertheless, as an initial preference, an attempt must be made to conform exactly to the plan mentioned below.

הלכה ד
וּשְׁלֹשָׁה נְבִיאִים עָלוּ עִמָּהֶם מִן הַגּוֹלָה. אֶחָד הֵעִיד לָהֶן עַל מְקוֹם הַמִּזְבֵּחַ. וְאֶחָד הֵעִיד לָהֶן עַל מִדּוֹתָיו. וְאֶחָד הֵעִיד לָהֶן שֶׁמַּקְרִיבִין עַל הַמִּזְבֵּחַ הַזֶּה כָּל הַקָּרְבָּנוֹת אַף עַל פִּי שֶׁאֵין שָׁם בַּיִת:
כסף משנה
4.
Three prophets returned to [Eretz Yisrael] with the people:13Chaggai, Zechariah, and Malachi. one attested to the site of the Altar;14For, as mentioned in Halachah 1, the Altar's site must be precise. the second, to its dimensions;15Note the previous halachah. and the third attested to [the Halachah permitting] all sacrifices to be offered on that Altar, even though the Temple itself was not [built] there [yet].16The Rambam's statements are taken from Zevachim 62a. However, the terminology in that source regarding Malachi's testimony is different. According to the Talmud, the prophet stated that "all the sacrifices may be offered, even though the Temple was not [built];" and the Rambam adds the phrase "on that Altar."
Later commentaries have explained the significance of that addition, based on the following episode. In the Middle Ages, the Sage, Rabbi Chayim (according to other sources, Rabbi Yechiel) of Paris made Aliyah and settled in Jerusalem. He wanted to offer sacrifices on the Temple Mount. In analyzing this account, the Chatam Sofer (Yoreh De'ah, Responsum 336) explained that this must have referred to the Pascal sacrifice, which could be offered in a state of ritual impurity and yet, did not have to be purchased with communal funds.
Among the reasons the commentaries have given why such a sacrifice could not be offered is that we are lacking an Altar with its proper size and dimensions. In contrast, the exiles who returned from Babylon were allowed to offer sacrifices on the altar built according to the prophets' directives.

הלכה ה
מִזְבֵּחַ שֶׁעָשָׂה משֶׁה וְשֶׁעָשָׂה שְׁלֹמֹה וְשֶׁעָשׂוּ בְּנֵי הַגּוֹלָה וְשֶׁעָתִיד לְהֵעָשׂוֹת כֻּלָּן עֶשֶׂר אַמּוֹת גֹּבַהּ כָּל אֶחָד מֵהֶן. וְזֶה הַכָּתוּב בַּתּוֹרָה (שמות כז א) "וְשָׁלֹשׁ אַמּוֹת קוֹמָתוֹ" מְקוֹם הַמַּעֲרָכָה בִּלְבַד. וּמִזְבֵּחַ שֶׁעָשׂוּ בְּנֵי הַגּוֹלָה וְכֵן הֶעָתִיד לְהִבָּנוֹת מִדַּת אָרְכּוֹ וְרָחְבּוֹ ל''ב אַמּוֹת עַל ל''ב אַמּוֹת:
כסף משנה
5.
The Altar constructed by Moses, and, [similarly,] that built by Solomon, and that erected by the [returning] exiles, and that to be built [in the Messianic age] are all ten cubits high.17See Ezekiel 43:13 and commentaries. Though the Torah states [Exodus 27:1]: "Its height will be three cubits," [that refers to] the surface on which the wood for the sacrifices was arranged.18See Zevachim 59b, which records a dispute among the Sages concerning the height of Moses' (and hence, all subsequent) Altar(s).
Among the proofs brought for the opinion accepted by the Rambam are the following:
a) an analogy drawn between the sacrificial altar and the incense altar. Just as the latter's height was twice its length, so, too, the height of the sacrificial altar (10 cubits) was twice its length (5 cubits).
b) The height of Moses' Altar had to equal that of the Sanctuary that accompanied the Jews in the desert, which was 10 cubits high.

The length and breadth of the Altar built by the [returning] exiles and, similarly, the one to be built in the Messianic Age, is 32 cubits by 32 cubits.19This measurement refers to the dimensions of the Altar's base and not to its upper surface, as explained in the following Halachah.

הלכה ו
עֶשֶׂר אַמּוֹת שֶׁל גֹּבַהּ הַמִּזְבֵּחַ מֵהֶן בְּאַמָּה בַּת חֲמִשָּׁה טְפָחִים וּמֵהֶן בְּאַמָּה בַּת שִׁשָּׁה טְפָחִים. וּשְׁאָר כָּל אַמּוֹת הַבִּנְיָן בְּאַמָּה בַּת שִׁשָּׁה טְפָחִים. וְגֹבַהּ כָּל הַמִּזְבֵּחַ נ''ח טְפָחִים:
כסף משנה
6.
The 10 cubits of the Altar's height [were not measured in a consistent manner.]20Kellim 17:10 relates that a cubit used in building was generally six handbreadths long. In contrast, the cubit used to measure utensils was five handbreadths long. An exception to this principle was made in regard to the Altar. Sometimes the measure of a "cubit" was six handbreadths, while in other cases, the cubit's measure was five handbreadths.21A handbreadth is the width of the four fingers of the hand when they are closed loosely. There is a debate among the Rabbis regarding the equivalent of this amount in modern measurements. Some authorities consider a handbreadth as 8 centimeters and others, as large as 9.6 centimeters. In all other cases, the cubits mentioned in the dimensions of the Temple are six handbreadths.
The height of the entire Altar22Including its horns. was 58 handbreadths.23I.e., two cubits were five handbreadths long, while the remaining eight were six handbreadths long, as explained in the following halachot.

הלכה ז
וְכָךְ הָיְתָה מִדָּתוֹ וְצוּרָתוֹ. עָלָה חֲמִשָּׁה טְפָחִים וְכָנַס חֲמִשָּׁה טְפָחִים זֶהוּ יְסוֹד. נִמְצָא רֹחַב שְׁלֹשִׁים אַמָּה וּשְׁנֵי טְפָחִים עַל רֹחַב שְׁלֹשִׁים אַמָּה וּשְׁנֵי טְפָחִים. עָלָה שְׁלֹשִׁים טְפָחִים וְכָנַס חֲמִשָּׁה טְפָחִים זֶהוּ סוֹבֵב [עָלָה י''ח טְפָחִים זֶהוּ מְקוֹם הַמַּעֲרָכָה] נִמְצָא רָחְבּוֹ שְׁמוֹנֶה וְעֶשְׂרִים אַמָּה וְאַרְבָּעָה טְפָחִים עַל שְׁמוֹנֶה וְעֶשְׂרִים אַמָּה וְאַרְבָּעָה טְפָחִים [עָלָה י''ח טְפָחִים וְכוֹנֵס לְקֶרֶן זָוִית שֶׁל הַי''ח בִּנְיָן חָלוּל מְרֻבָּע לְכָל אַרְבַּע קְרָנוֹת] וּמְקוֹם הַקְּרָנוֹת אַמָּה מִזֶּה וְאַמָּה מִזֶּה סָבִיב. וְכֵן מְקוֹם רַגְלֵי הַכֹּהֲנִים אַמָּה סָבִיב. נִמְצָא מְקוֹם הַמַּעֲרָכָה רָחְבּוֹ עֶשְׂרִים וְאַרְבַּע אַמּוֹת וְאַרְבָּעָה טְפָחִים עַל עֶשְׂרִים וְאַרְבַּע אַמּוֹת וְאַרְבָּעָה טְפָחִים:
כסף משנה
7.
The [Altar's] dimensions and design were as follows:24The Rambam actually included a diagram in his text of the Mishneh Torah. The accompanying diagram is based on the Rambam's original.
This entire Halachah is based on the Rambam's interpretation of Ezekiel's vision. Rashi interprets that prophecy differently, and many Rabbinic opinions follow his view. See the Kessef Mishneh and other commentaries.
Five handbreadths up and five handbreadths in25In this instance, five handbreadths were considered as a cubit. [form a step called] the base. Thus, the [remaining area of the Altar] was 30 cubits and two handbreadths by 30 cubits and two handbreadths.26As mentioned above, the Altar was 32 cubits long and 32 cubits wide. Each cubit was six handbreadths long. When the five handbreadths of the base were subtracted from each side, the following equation determines the remaining length and width: 32 cubits minus 10 (i.e., 5 on either side) handbreadths, equals 30 cubits and two handbreadths.
Thirty handbreadths [further] up and 5 handbreadths [further] in is [called] the surrounding ledge.27This name was chosen because, in contrast to the base, the ledge surrounded the altar on all four sides (Tifferet Yisrael).
The height of thirty handbreadths is considered as five cubits, for this cubit is measured by six handbreadths.

Thus, its area was 28 cubits and four handbreadths by 28 cubits and four handbreadths.28This figure is reached when 10 handbreadths (5 on either side) are subtracted from 30 cubits and 2 handbreadths.
Go up eighteen handbreadths, place a hollow, rectangular structure in each corner of this surface [thus, creating the Altar's] four horns.
The area encompassed by the horns was one cubit by one cubit on all sides.29In this case, the cubits contained six handbreadths. Each of the horns was a cubit long and a cubit wide. The space in between them was left hollow, thus, reducing both the length and the width of the upper surface of the altar by two cubits. Similarly, the space for the priests to walk was a cubit on all sides.30Here too, the cubit had six handbreadths, thus reducing both the length and the width of the upper surface of the altar by two cubits.
[Thus,] the surface on which [the wood for the sacrifices] was arranged31I.e., the upper surface of the altar. was 24 cubits and four handbreadths by 24 cubits and four handbreadths.32The Ra'avad explains that the Altar's horns were slanted inward, thus, consuming an additional four handbreadths of space and reducing the surface to exactly 24 cubits. It must be noted that both Rashi and Tosefot (Sukkah 45a) concur with the Rambam's opinion that the horns stood directly perpendicular to the Altar.

הלכה ח
גֹּבַהּ כָּל קֶרֶן וְקֶרֶן חֲמִשָּׁה טְפָחִים. וְרִבּוּעַ כָּל קֶרֶן אַמָּה עַל אַמָּה. וְאַרְבַּע הַקְּרָנוֹת חֲלוּלוֹת הָיוּ מִתּוֹכָן. וְגֹבַהּ מְקוֹם הַמַּעֲרָכָה י''ח טְפָחִים. נִמְצָא חֲצִי גֹּבַהּ הַמִּזְבֵּחַ כ''ט טְפָחִים מִסּוֹף הַסּוֹבֵב וּלְמַטָּה:
כסף משנה
8.
Each horn was five handbreadths high.33The horns were a cubit high when using the measure of five handbreadths to the cubit. The area of each horn was a cubit by a cubit. [All] four horns were hollow.34Zevachim 54b derives this concept as follows: The prophet Zechariah declared: "And they shall be filled like bowls, like the corners of the Altar." Thus, that vision implies that the horns located on the Altar's corners can serve as receptacles.
Thus, the surface on which [the wood for the sacrifices] was arranged was 18 handbreadths above [the surrounding ledge.]
Half of the Altar's height [began] 6 handbreadths below the end of the surrounding ledge.35The height of the altar can be summarized as follows:
a) the base - 1 cubit - 5 handbreadths
b) the surrounding ledge - 5 cubits - 30 handbreadths
c) the Altar's surface - 3 cubits - 18 handbreadths
d) the horns - 1 cubit - 5 handbreadths, a total of 58 handbreadths. Thus half of its height was 29 handbreadths. The surrounding ledge was 30 cubits high and the base, five. Thirty plus five minus six equals 29.

הלכה ט
וְחוּט שֶׁל סִקְרָה הָיָה חוֹגֵר בְּאֶמְצַע הַמִּזְבֵּחַ [כְּשִׁשָּׁה טְפָחִים מִסּוֹף הַסּוֹבֵב וּלְמַטָּה] לְהַבְדִּיל בֵּין דָּמִים הָעֶלְיוֹנִים לְדָמִים הַתַּחְתּוֹנִים. וְנִמְצָא גָּבְהוֹ מִן הָאָרֶץ עַד מְקוֹם הַמַּעֲרָכָה תֵּשַׁע אַמּוֹת פָּחוֹת טֶפַח:
כסף משנה
9.
A scarlet band36The altar in the Sanctuary in the desert had a copper net screen which served this function. See Exodus 27:4-5 and Zevachim 53a. is girded around the middle of the Altar six handbreadths below the surrounding ledge to separate between the blood [to be cast on] the upper [portion of the Altar]37The blood of a fowl brought as a burnt offering had to be cast on the upper portion of the Altar (Hilchot Ma'aseh HaKorbanot 6:20). and the blood [to be sprinkled on] the lower [portion of the Altar].38The blood of a bird brought as a sin offering was sprinkled on the lower portion of the Altar (ibid. 7:6). Similarly, the blood of animals brought as burnt, guilt, or peace offerings was sprinkled in the same place (ibid. 5:6).
Thus, the distance from the earth to the surface on which [the wood for the sacrifices] was arranged was a handbreadth less than nine cubits.39As mentioned above, the Altar's horns were 1 cubit high. Thus, one cubit may be subtracted from the ten cubit height mentioned previously. Since the Altar's base measured five handbreadths and not six, an additional handbreadth is subtracted, leaving the figure mentioned in this Halachah.

הלכה י
יְסוֹד הַמִּזְבֵּחַ לֹא הָיָה מַקִּיף מֵאַרְבַּע רוּחוֹתָיו כְּמוֹ הַסּוֹבֵב. אֶלָּא הָיָה הַיְסוֹד מָשׁוּךְ כְּנֶגֶד כָּל רוּחַ צָפוֹן וּמַעֲרָבִי וְאוֹכֵל בַּדָּרוֹם אַמָּה אַחַת וּבַמִּזְרָח אַמָּה אַחַת. וְקֶרֶן דְּרוֹמִית מִזְרָחִית לֹא הָיָה לָהּ יְסוֹד:
כסף משנה
10.
The ledge encircled the Altar on all four sides. The base did not.40Zevachim 53b explains that although a major portion of the Temple Mount was in Judah's inheritance, the Altar was to be positioned in the tribal inheritance of Benjamin. (Note the Targum on Genesis 49:27.)
A small stretch of land extended out of the inheritance of Judah into that of Benjamin, and occupied a portion of the space that should have been taken by the Altar's base. That space was left empty to insure that the entire structure of the Altar was in the inheritance of Benjamin. Note the commentary to Chapter 7, Halachah 14.
The base encompassed the entire northern41The side to one's right as one faced the Holy of Holies. and western42The side of the Altar closest to the Temple building. sides [of the Altar], and consumed one cubit on the South side and one cubit on the east side.43Thus the Altar's base only extended one cubit on each of its southern and eastern sides.
This interpretation of the Rambam's text is based on the diagrams accompanying his commentary on the Mishnah published by Rav Kapach. Rashi's commentary (Zevachim, ibid. ) expresses the same concept. See the accompanying diagram.
[Thus,] the southeast corner [of the Altar] did not have a base.

הלכה יא
וּבְקֶרֶן מַעֲרָבִית דְּרוֹמִית הָיוּ שְׁנֵי נְקָבִים כְּמִין שֵׁנִי חֳטָמִין דַּקִּין. וְהֵן הַנִּקְרָאִין שִׁיתִין שֶׁהַדָּמִים יוֹרְדִין בָּהֶן וּמִתְעָרְבִין בְּאוֹתָהּ הַקֶּרֶן בָּאַמָּה וְיוֹצְאִין לַנַּחַל קִדְרוֹן:
כסף משנה
11.
There were two holes in the southwest corner [of the Altar's base],44The blood from the sacrifices was either poured on the south or the west side of the Altar, depending on the nature of the offering. These holes were positioned in the southwest corner to facilitate drainage. (See the Rambam's Commentary to the Mishnah, Middot 3:2.) resembling two thin nostrils. They were called Shittin.45That name was derived from the word shotet meaning "flow." The blood from the Altar flowed away through these holes. The blood46And also the wine and water libations (see Hilchot Temidim UMusafim 10:7). [which was poured onto the Altar] would run off through them and be mixed together in the drainage canal in that corner.47The drainage canal passed through the entire Temple courtyard and was used when the priests wanted to clean the courtyard floor. They would plug the drain, flooding the entire courtyard with water, and then unplug the drain and let the water flow out through the canal. From there, it would flow out to the Kidron River.48Because of the large amount of blood that would flow into that river, its water was sold as fertilizer (Commentary of the Rosh to Middot, ibid.).

הלכה יב
וּלְמַטָּה בָּרִצְפָּה בְּאוֹתוֹ הַקֶּרֶן הָיָה מְקוֹם אַמָּה עַל אַמָּה וְטַבְלָא שֶׁל שַׁיִשׁ וְטַבַּעַת קְבוּעָה בָּהּ שֶׁבּוֹ יוֹרְדִין לַשִּׁיתִין וּמְנַקִּין אוֹתוֹ:
כסף משנה
12.
Below, in the floor of that corner of the Altar, was a place, a cubit by a cubit, [covered by] a block of marble, with a ring affixed to it.49The ring facilitated the lifting of the marble block. They would descend there to the Shittin and clean them.50Lest the blood coagulate and cause them to become clogged.

הלכה יג
וְכֶבֶשׁ הָיָה בָּנוּי לִדְרוֹמוֹ שֶׁל מִזְבֵּחַ. אָרְכּוֹ שְׁלֹשִׁים וּשְׁתַּיִם אַמָּה עַל רֹחַב ט''ז אַמָּה וְהָיָה אוֹכֵל בָּאָרֶץ שְׁלֹשִׁים אַמָּה מִצַּד הַמִּזְבֵּחַ. וּפוֹרֵחַ מִמֶּנָּה אַמָּה עַל הַיְסוֹד וְאַמָּה עַל הַסּוֹבֵב. וַאֲוִיר מְעַט הָיָה מַפְסִיק בֵּין הַכֶּבֶשׁ לַמִּזְבֵּחַ כְּדֵי לִתֵּן הָאֵיבָרִים לַמִּזְבֵּחַ בִּזְרִיקָה. וְגֹבַהּ הַכֶּבֶשׁ תֵּשַׁע אַמּוֹת פָּחוֹת שְׁתוּת עַד כְּנֶגֶד הַמַּעֲרָכָה:
כסף משנה
13.
The ramp51See Chapter 1, Halachah 17. was constructed to the south of the Altar.52I.e., on one's left when facing the Holy of Holies. Its length was 32 cubits, and its width, sixteen cubits. It consumed 30 cubits on the ground adjacent to the Altar, and extended [further, covering] one cubit of the base and one cubit of the surrounding ledge.53The ramp was not built as a right triangle. Rather, the wall on the right side was slanted slightly, so that the ramp would cover the base and the surrounding ledge, which together protruded two cubits beyond the edge of the Altar itself.
The phrase "its length" does not refer to the length of the ramp's surface, (the hypotenuse of the triangle), but the space it occupied on the ground, as well as the two additional cubits with which it overlapped the base and the surrounding ledge. The actual length of the ramp's surface was slightly longer.

There was a small space54Larger than the hair's breadth mentioned in the following halachah. between the ramp and the Altar so that the limbs [of the sacrifices] would have to be tossed to reach the Altar.55The wood piles upon which the Altar's fire were to be kindled were arranged on the south side of the Altar, so that the priests would be able to ascend the ramp and place the sacrificial limbs directly on those pyres. However, the ramp did not reach the edge of the Altar. The priests were thus prevented from placing the limbs directly on the fire and were required to toss them.
Zevachim 62b explains the necessity to toss the limbs, as follows: The Torah draws an analogy between the flesh of an offering and its blood, as it is written (Deuteronomy 12:27 : "You shall sacrifice your burnt offerings, the flesh and the blood." The blood must be tossed on the Altar, as it is written (Leviticus 1:5 : "And they shall toss the blood on the Altar." Hence, the limbs must also reach the pyre in that fashion.
See also Hilchot Ma'aseh HaKorbanot 6:4.

The height of the ramp was nine cubits minus a sixth of a cubit. It equaled that of [the surface on which the wood for the sacrifices] was arranged.56As mentioned in Halachah 7, the cubit measurement for the base had only five handbreadths. Thus, the Altar's - and consequently, the ramp's - height was eight and five-sixths cubits, when calculated in cubits of six handbreadths.
The Rambam's phrasing at the beginning of the Halachah, "[covering] one cubit of the base and one cubit of the surrounding ledge" requires clarification, because the base itself did not run under the ramp. However, the space for it was left vacant.
See the accompanying diagram for a depiction of the concepts mentioned in this Halachah.

הלכה יד
וּשְׁנֵי כְּבָשִׁים קְטַנִּים יוֹצְאִים מִמֶּנּוּ שֶׁבָּהֶם פּוֹנִים לַיְסוֹד וְלַסּוֹבֵב וּמֻבְדָּלִין מִן הַמִּזְבֵּחַ כִּמְלֹא נִימָא. וְחַלּוֹן הָיְתָה בְּמַעֲרָבוֹ שֶׁל כֶּבֶשׁ אַמָּה עַל אַמָּה וּרְבוּבָה הָיְתָה נִקְרֵאת. שֶׁבָּהּ נוֹתְנִין פְּסוּלֵי חַטַּאת הָעוֹף עַד שֶׁתַּעֲבֹר צוּרָתָהּ וְתֵצֵא לְבֵית הַשְּׂרֵפָה:
כסף משנה
14.
Two small ramps extended from it. One led to the base,57This small ramp was placed on the west side of the altar, the side closest to the Temple building. After the blood of the sin offerings were sprinkled as required, the rest of the blood was poured on the west side of the Altar's base. This ramp allowed the priests to reach that position. and the other to the surrounding ledge.58The ramp leading to the surrounding ledge was on the east side of the Altar. When the priests circled the Altar to sprinkle the blood of the sin offering on the Altar's horns, they ascended using this ramp.
The above follows the opinion expressed by Rashi (Zevachim, loc. cit.). Some other authorities maintain that both smaller ramps were situated on the west side of the Altar. Though the Rambam does not state his opinion explicitly, from his description of the sacrificial proceedings (Hilchot Ma'aseh HaKorbanot: 6:20, 7:10), it appears that he accepts the first opinion.
They were set off from the Altar by a hair's breadth.
There was an aperture on the west side59The aperture was placed there because sin-offerings were offered on the southwest corner of the Altar (Rashi, Pesachim 34a).
It appears that this aperture was located on the wall of the ramp, and not on its upper surface (Tifferet Yisrael).
of the ramp, a cubit by a cubit. It was called the Rivuvah.6013Rav Ovadiah of Bartinura explains that this word means "hollow place."
The Ra'avad explains that there were two openings: one called the aperture, and the second, the Rivuvah. His opinion is not accepted by most authorities, as explained in the Kessef Mishneh.
There, fowl that had been disqualified for use as sin offerings would be placed until their form decomposed, at which time they could be taken out to be burnt.61Generally, a sin-offering that is disqualified for use must be removed from the Altar and burned immediately. However, if there are no severe factors to invalidate the sacrifice, it would appear disrespectful to dispose of the sacrifice in that manner. Rather, the sacrifice is left overnight - an act which obligates a sacrifice to be removed and burnt - and disposed of the next morning (Rashi, loc. cit..).
A woman who gave birth was obligated to bring a bird as a sin offering. Hence, it was a very common sacrifice. The Rivuvah was constructed to store the birds which had become disqualified. It thus prevented confusion between those birds which were disqualified, and those which were fit to be sacrificed (Tifferet Yisrael).

הלכה טו
וּשְׁנֵי שֻׁלְחָנוֹת הָיוּ בְּמַעֲרַב הַכֶּבֶשׁ אֶחָד שֶׁל שַׁיִשׁ שֶׁנּוֹתְנִין עָלָיו אֶת הָאֵיבָרִים וְאֶחָד שֶׁל כֶּסֶף שֶׁנּוֹתְנִין עָלָיו כְּלֵי הַשָּׁרֵת:
כסף משנה
15.
Two tables were [placed] on the left side of the ramp:
One of marble, on which the limbs [of the sacrifices to be offered on the Altar] were placed,62The communal sacrifices were brought directly from the slaughtering area to the top of the Altar by a number of priests. Thus, there was no need to set aside a place for the limbs to be placed. However, sometimes private sacrifices were offered by only one priest, who could not possibly carry all the limbs at one time. This table was useful on such occasions.
Though generally an effort was made to use precious metals in the Temple, this table was made of marble. The sages feared that a metal table would conduct heat and cause the sacrificial meat to spoil. Marble is better for this purpose, since it is a very poor conductor of heat. See Shekalim 6:4, and Tamid 31b.
and
One of silver, on which sacrificial vessels were placed.

הלכה טז
כְּשֶׁבּוֹנִין הַמִּזְבֵּחַ בּוֹנִין אוֹתוֹ כֻּלּוֹ אָטוּם כְּמִין עַמּוּד וְאֵין עוֹשִׂין בּוֹ חָלָל כְּלָל. אֶלָּא מֵבִיא אֲבָנִים שְׁלֵמוֹת גְּדוֹלוֹת וּקְטַנּוֹת וּמֵבִיא סִיד וְזֶפֶת וְקוּנְיָא וּמְמַחֶה וְשׁוֹפַךְ לְתוֹךְ מַלְבֵּן גָּדוֹל כְּמִדָּתוֹ וּבוֹנֶה וְעוֹלֶה. וְנוֹתֵן בְּתוֹךְ הַבִּנְיָן גּוּף שֶׁל עֵץ אוֹ אֶבֶן בְּקֶרֶן דְּרוֹמִית מִזְרָחִית כְּמִדַּת הַיְסוֹד. וְכֵן נוֹתֵן בְּתוֹךְ כָּל קֶרֶן וְקֶרֶן עַד שֶׁיַּשְׁלִים הַבִּנְיָן וְיָסִיר הַגּוּפִים שֶׁבְּתוֹךְ הַבִּנְיָן כְּדֵי שֶׁתִּשָּׁאֵר קֶרֶן דְּרוֹמִית מִזְרָחִית בְּלֹא יְסוֹד וְיִשָּׁאֲרוּ הַקְּרָנוֹת חֲלוּלִין:
כסף משנה
16.
When we build the Altar, it must be made as one solid block, resembling a pillar. No empty cavity may be left at all.63In the sanctuary of the desert, the Altar was a hollow structure filled with earth (Exodus 27:8, Mechilta). However, such a structure was not acceptable for the Temple.
We must bring whole stones, both large and small.64See Chapter 1, Halachot 14-16. Then we must create a liquid with lime, pitch, and molten lead, and pour it [over the stones] into a large mold of its dimensions.65As mentioned in the following halachah, the Altar must be entirely square, yet we were forbidden to cut or file it to size. Wooden molds were employed in order to create such a shape. We must build it in this manner, ascending [level by level].66Zevachim 54a describes the Altar's construction in detail: First, a mold 32 cubits by 32 cubits, and one cubit high, was brought to create the base. The mixture of stones, lime, pitch, and molten lead was poured into it. Then, the mold for the second level, the surrounding ledge, was placed down. This mold was 30 cubits by 30 cubits and five cubits high. After the mixture was poured into it, the mold for the Altar's upper surface was brought. That mold, 28 cubits by 28 cubits, was three cubits high. Once it was filled, four molds, each a cubit by a cubit and one cubit high, were placed in each corner for the horns.
The measures mentioned above were all rounded off. As mentioned in Halachot 6-7, additional handbreadths must be added or subtracted for all these measures.

We must place a block of wood or stone in the southeast corner of the structure, equal to the measure of [the missing portion of the Altar's] base.67See Halachah 10. Similarly, [blocks] must be placed in each horn until the building is completed.68For the horns must be hollow, as mentioned in Halachah 8. Then, the blocks may be removed from the structure, thus leaving the southeast corner without a base, and the horns, hollow.

הלכה יז
אַרְבַּע קְרָנוֹת שֶׁל מִזְבֵּחַ וִיסוֹדוֹ וְרִבּוּעוֹ מְעַכְּבִין. וְכָל מִזְבֵּחַ שֶׁאֵין לוֹ קֶרֶן יְסוֹד וְכֶבֶשׁ וְרִבּוּעַ הֲרֵי הוּא פָּסוּל שֶׁאַרְבַּעְתָּן מְעַכְּבִין. אֲבָל מִדַּת אָרְכּוֹ וּמִדַּת רָחְבּוֹ וּמִדַּת קוֹמָתוֹ אֵינָן מְעַכְּבִין. וְהוּא שֶׁלֹּא יִפְחֹת מֵאַמָּה עַל אַמָּה בְּרוּם שָׁלֹשׁ אַמּוֹת כְּשִׁעוּר מְקוֹם הַמַּעֲרָכָה שֶׁל מִזְבַּח מִדְבָּר:
כסף משנה
17.
The four horns, the base, and a square shape are absolute requirements for the Altar. Any Altar which lacks [either] a horn, a base, a ramp, or a square shape, is unfit for use, for these four are absolute requirements.69Regarding these four elements, the Torah uses the expression hamizbeiach, the Altar, implying that the Altar can only be called an Altar if it possesses these elements. If even one is lacking, the Altar is incomplete (Rashi, Zevachim, 62a):
In regard to the horns, it is written (Leviticus 4:18 : "the horns of the Altar."
In regard to the base, it is written (ibid.:34): "to the base of the Altar."
In regard to the ramp, it is written (ibid. 6:7): "to the face of the Altar." This phrase refers to the ramp, for it faces the Altar and allows access to it.
In regard to the Altar's square shape, it is written (Exodus 27:1 : "The Altar shall be square."

However, the measures of length, width, and height, are not absolute requirements,70See Halachah 3. provided they are not less than a cubit by a cubit [in area,] and three cubits high. [The latter were] the dimensions of the surface [on which the wood for the sacrifices] was arranged for the altar [in the Sanctuary that accompanied the Jews] in the desert.71See Halachah 5.

הלכה יח
מִזְבֵּחַ שֶׁנִּפְגַּם מִבִּנְיָנוֹ אִם נִפְגַּם מִבִּנְיָנוֹ טֶפַח פָּסוּל פָּחוֹת מִטֶּפַח כָּשֵׁר וְהוּא שֶׁלֹּא יִהְיֶה בַּנִּשְׁאָר אֶבֶן פְּגוּמָה:
כסף משנה
18.
[The following laws apply when] the structure of the Altar is damaged. If a handbreadth of its structure is damaged, it is unfit for use.72In Chapter 1, Halachah, the Rambam writes: "Any stone which is damaged to the extent that a nail will become caught in it [when passing over it], as is the case regarding a slaughtering knife, is disqualified for [use in the] Altar or the ramp, as it is written (Deuteronomy 27:6 : 'You shall build the Altar of the Lord with whole stones.'
The Kessef Mishneh explains that since the Torah requires whole stones to be used for the Altar, even the slightest damage renders them unfit for use. In contrast, the Torah does not make such a specification regarding the Altar itself. Hence, as long as the damage is not extensive, the Altar is not disqualified.
If less than a handbreadth [is damaged], it is acceptable,73Chullin 18a records a debate on this subject, between Rabbi Shimon bar Yochai and Rabbi Elazer ben Yaakov. Rabbi Shimon mentions the measure quoted by the Rambam, while Rabbi Elazer maintains that even smaller damage, the size of an olive, can render the Altar unfit for use. Though generally, halachah is usually decided according to Rabbi Elazer's opinion, the Rambam chose that of Rabbi Shimon. provided none of the remaining stones are damaged.74As mentioned above, the Altar is rendered unfit if there is the slightest damage to its stones.

עבודה הלכות בית הבחירה פרק ב
Avodah Bet HaBechirah Chapter 2