Halacha

הלכה א
הָאוֹכֵל כְּזַיִת חֵלֶב בְּמֵזִיד חַיָּב כָּרֵת. בְּשׁוֹגֵג מֵבִיא חַטָּאת קְבוּעָה. וּבְפֵרוּשׁ אָמְרָה תּוֹרָה שֶׁאֵינוֹ חַיָּב אֶלָּא עַל שְׁלֹשָׁה מִינֵי בְּהֵמָה טְהוֹרָה בִּלְבַד שֶׁנֶּאֱמַר (ויקרא ז כג) "כָּל חֵלֶב שׁוֹר וְכֶשֶׂב וָעֵז לֹא תֹאכֵלוּ" בֵּין שֶׁאָכַל מֵחֵלֶב שְׁחוּטָה בֵּין שֶׁאָכַל מֵחֵלֶב נְבֵלָה וּטְרֵפָה שֶׁלָּהֶן. אֲבָל שְׁאָר בְּהֵמָה וְחַיָּה בֵּין טְמֵאָה בֵּין טְהוֹרָה חֶלְבָּהּ כִּבְשָׂרָהּ. וְכֵן נֵפֶל שֶׁל שְׁלֹשָׁה מִינֵי בְּהֵמָה טְהוֹרָה חֶלְבּוֹ כִּבְשָׂרוֹ וְהָאוֹכֵל מֵחֶלְבּוֹ כְּזַיִת לוֹקֶה מִשּׁוּם אוֹכֵל נְבֵלָה:
כסף משנה
1.
When a person willfully eats an olive-sized portion of forbidden fat,1The term forbidden fat refers to the Hebrew term cheilev, to distinguish it from shuman which refers to fat that may be eaten. Unless otherwise mentioned, the term "fat" in this text will refer to forbidden fat. he is liable for kerat. If he partakes of it inadvertently, he must bring a fixed sin-offering.
It is explicitly stated in the Torah that he is liable for partaking2There is, however, no prohibition against benefiting from forbidden fat. See Chapter 8, Halachah 15. [of the fat] of the three species of kosher domesticated animals alone, as [Leviticus 7:23] states: "Do not partake of any fat from an ox, lamb, or goat."3Sefer HaMitzvot (negative commandment 185) and Sefer HaChinuch (mitzvah 147) include this prohibition among the 613 mitzvot of the Torah. [This applies] whether one partakes of fat from an animal that is ritually slaughtered or one partakes of fat from a nevelah or a trefe [from a kosher species].4See the following halachah. With regard to other domesticated animals and wild beasts, whether non-kosher or kosher, their fat is comparable to their meat.5I.e., there is no separate prohibition concerning it. If the animal is kosher, its fat is not considered cheilev and is permitted. If the animal is not-kosher, its fat is of course forbidden, but it is not bound by a separate prohibition. This reflects a contrast to the prohibition against partaking of blood mentioned in the previous chapter. Similarly, the fat of a stillborn fetus of the three species of kosher animals is comparable to its flesh. When one partakes of an olive-sized portion of it, one is liable for lashes for partaking of a nevelah.6There is not, however, a separate prohibition for partaking of its forbidden fat. From Chulin 75a, it appears that this leniency applies only when the fetus is stillborn before its full period of gestation is completed. If, however, the full period of gestation is completed, the prohibition against cheilev does apply (Maggid Mishneh; Siftei Cohen 64:5). See also Halachot 3-4.

הלכה ב
הָאוֹכֵל מֵחֵלֶב נְבֵלָה וּטְרֵפָה חַיָּב מִשּׁוּם אוֹכֵל חֵלֶב וּמִשּׁוּם אוֹכֵל נְבֵלָה וּטְרֵפָה מִתּוֹךְ שֶׁנּוֹסָף הָאִסּוּר בִּבְשָׂרָהּ שֶׁהָיָה מֻתָּר נוֹסָף עַל הַחֵלֶב וּלְפִיכָךְ לוֹקֶה שְׁתַּיִם:
כסף משנה
2.
When a person partakes of the fat of a nevelah or a trefe, he is liable for partaking of fat and for partaking of a nevelah or a trefe. [The rationale]7I.e., why we do not follow the principle that one prohibition does not fall upon another. is that since a prohibition is added to its meat - for it was permitted beforehand - it is also added to its fat.8The fat was forbidden previously and a further prohibition is added when the meat becomes forbidden. Hence one is liable for two sets of lashes.

הלכה ג
הַשּׁוֹחֵט בְּהֵמָה וּמָצָא בָּהּ שָׁלִיל כָּל חֶלְבּוֹ מֻתָּר וַאֲפִלּוּ מְצָאוֹ חַי מִפְּנֵי שֶׁהוּא כְּאֵיבָר מִמֶּנָּה. וְאִם שָׁלְמוּ לוֹ חֳדָשָׁיו וּמְצָאוֹ חַי אַף עַל פִּי שֶׁלֹּא הִפְרִיס עַל הַקַּרְקַע וְאֵינוֹ צָרִיךְ שְׁחִיטָה חֶלְבּוֹ אָסוּר וְחַיָּבִין עָלָיו כָּרֵת. וּמוֹצִיאִין מִמֶּנּוּ כָּל הַחוּטִין וְהַקְּרוּמוֹת הָאֲסוּרִין כִּשְׁאָר הַבְּהֵמוֹת:
כסף משנה
3.
When a person slaughters an animal and finds a fetus in its womb, all of its fat is permitted.9Contrast this to the prohibition against gid hanasheh as stated in Chapter 8, Halachah 1. [This applies] even if the fetus is alive, because it is considered as a limb of [the mother]. If it was carried for the full period of gestation and discovered to be alive, its fat is forbidden and one is liable for kerat for partaking of it. [This applies] even if [the fetus] never stepped on the ground and does not require ritual slaughter.10As stated in Chapter 5, Halachah 14. The Ra'avad mentions an opinion which states that one is not liable. The Shulchan Aruch (Yoreh De'ah 64:2) cites both views.. [Instead,] we must remove all the forbidden strands of tissue and membranes from it as [is required] with regard to other animals.

הלכה ד
הוֹשִׁיט יָדוֹ לִמְעֵי בְּהֵמָה וְחָתַךְ מֵחֵלֶב הָעֻבָּר שֶׁכָּלוּ לוֹ חֳדָשָׁיו וְהוֹצִיאוֹ הֲרֵי זֶה חַיָּב עָלָיו כְּאִלּוּ חֲתָכוֹ מֵחֵלֶב הָאֵם עַצְמָהּ. שֶׁהֶחֳדָשִׁים הֵן הַגּוֹרְמִין לְאִסּוּר הַחֵלֶב:
כסף משנה
4.
When a person inserts his hand into an animal's womb and cuts off and takes out the fat of a fetus that has undergone a full period of gestation, he is liable11From the Rambam's inclusion of the phrase "takes out," the Kessef Mishneh concludes that the prohibition applies only when the fat is taken out from the mother's womb while the animal is still alive. If the fat is left inside the womb and then the animal is slaughtered, he maintains that the fat is permitted. This conclusion is cited by the Turei Zahav 64:4 and the Siftei Cohen 64:6. for it in the same way as if he cut off the fat of the animal itself. [The rationale is that the fulfillment of the gestation period] is what causes the prohibition against fat.12The Maggid Mishneh clarifies that this stringency does not apply when the fetus dies in its mother's womb even if it has completed the nine months of gestation.

הלכה ה
שְׁלֹשָׁה חֲלָבִים הֵן שֶׁחַיָּבִין עֲלֵיהֶן כָּרֵת. חֵלֶב שֶׁעַל הַקֶּרֶב וְשֶׁעַל שְׁתֵּי הַכְּלָיוֹת וְשֶׁעַל הַכְּסָלִים. אֲבָל הָאַלְיָה מֻתֶּרֶת בַּאֲכִילָה. לֹא נִקְרֵאת חֵלֶב אֶלָּא לְעִנְיַן קָרְבָּן בִּלְבַד כְּמוֹ שֶׁנִּקְרְאוּ חֲלָבִים כְּלָיוֹת וְיוֹתֶרֶת הַכָּבֵד לְעִנְיַן קָרְבָּן. כְּמוֹ שֶׁאַתָּה אוֹמֵר (בראשית מה יח) "חֵלֶב הָאָרֶץ" וְ(דברים לב יד) "חֵלֶב כִּלְיוֹת חִטָּה" שֶׁהוּא טוּבָם. וּלְפִי שֶׁמְּרִימִין דְּבָרִים אֵלּוּ מִן הַקָּרְבָּן לִשְׂרֵפָה לַשֵּׁם נִקְרְאוּ חֵלֶב. שֶׁאֵין שֵׁם דָּבָר טוֹב אֶלָּא הַמּוּרָם לַשֵּׁם. וּלְכָךְ נֶאֱמַר בִּתְרוּמַת מַעֲשֵׂר (במדבר יח ל לב) "בַּהֲרִימְכֶם אֶת חֶלְבּוֹ מִמֶּנּוּ":
כסף משנה
5.
There are three types of forbidden fat for which one is liable for kerat: the fat on the digestive organs, on both kidneys, and on the flanks. The fat-tail, by contrast, is permitted to be eaten.13The Shulchan Aruch (Yoreh De'ah 64:5) states that one must remove the fatty portion on the inner side. It is called fat only with regard to the sacrifices, just as the kidneys and the large lobe of the liver are referred to as "fat" with regard to the sacrifices.14Chulin 117a interprets Leviticus 3:16: "All of the cheilev to God" as referring to the portions of the animal offered on the altar. These include the kidneys and the lobe of the liver although they are not "fat" (see Hilchot Maaseh HaKorbanot 1:18). Instead, the intent of term cheilev in the verse is "choice portions." Similarly, we find the expressions15Genesis 45:18; Deuteronomy 32:14. "the fat of the land," and "wheat as fat as kidneys" [where the intent is not "fat,"] but "choice."
Since these entities are being raised up from the sacrifice to be consumed with fire for God, they are called "the fat," i.e., the choice portion, for there is nothing more choice than the portion consumed with fire for God. For this reason, with regard to terumat ma'aser16The tenth of the tithe which the Levites who receive the tithe must separate and give the priests. [Numbers 18:30] states: "When you raise up its fat from it."17Here also the intent of the term cheilev is "choice portions."

הלכה ו
חֵלֶב שֶׁעַל הֶמְסֵס וְשֶׁעַל בֵּית הַכּוֹסוֹת הוּא הַחֵלֶב שֶׁעַל הַקֶּרֶב. וְחֵלֶב שֶׁבְּעִקְּרֵי הַיְרֵכוֹת מִבִּפְנִים חַיָּבִין עָלָיו כָּרֵת וְהוּא הַחֵלֶב שֶׁעַל הַכְּסָלִים. וְיֵשׁ שָׁם חֵלֶב עַל הַקֵּבָה עָקֹם כְּמוֹ קֶשֶׁת וְהוּא הָאָסוּר וְחוּט מָשׁוּךְ כְּמוֹ יֶתֶר וְהוּא מֻתָּר. חוּטִין שֶׁבַּחֵלֶב אֲסוּרִין וְאֵין חַיָּבִין עֲלֵיהֶן כָּרֵת:
כסף משנה
6.
The fat on the abdomen18An animal has four stomachs. We have chosen synonyms arbitrarily to describe them. and on the gut is what is meant by the term "the fat on the digestive organs." One is liable for the fat at the joints of the thighs on the inside. This is what is meant by the term "the fat on the flanks." There is also fat on the maw which is bent like an arch; it is forbidden. There is a ligament that extends like a lobe; it is permitted. The strands [stemming from] the fat are forbidden, but one is not liable for kerat for them.

הלכה ז
חֵלֶב שֶׁהַבָּשָׂר חוֹפֶה אוֹתוֹ מֻתָּר. שֶׁעַל הַכְּסָלִים אָסַר הַכָּתוּב לֹא שֶׁבְּתוֹךְ הַכְּסָלִים. וְכֵן חֵלֶב שֶׁעַל הַכְּלָיוֹת נֶאֱסַר וְלֹא שֶׁבְּתוֹךְ הַכְּלָיוֹת. וְאַף עַל פִּי כֵּן נוֹטֵל אָדָם לֹבֶן שֶׁבְּתוֹךְ הַכּוּלְיָא וְאַחַר כָּךְ אוֹכֵל אוֹתָהּ וְאֵינוֹ צָרִיךְ לְחַטֵּט אַחֲרָיו:
כסף משנה
7.
Fat which is covered by meat is permitted. Scripture forbids "fat on the flanks," but not within the flanks. Similarly, "fat on the kidneys" is forbidden, but not fat within the kidneys. Nevertheless, a person should remove the white matter within the kidney and only then, partake of it. It is not necessary, however, to remove all traces of it.19The Shulchan Aruch (Yoreh De'ah 64:12) cites the Rambam's view, but also that of the Tur which requires one to be stringent and remove all of its traces. The Rama states that, after the fact, even the stringent opinions do not consider the kidney forbidden if it was cooked without the traces of this fat being removed.

הלכה ח
יֵשׁ כְּמוֹ שְׁתֵּי פְּתִילוֹת שֶׁל חֵלֶב בְּעִקְּרֵי הַמָּתְנַיִם סָמוּךְ לְרֹאשׁ הַיָּרֵךְ. כְּשֶׁהַבְּהֵמָה חַיָּה חֵלֶב זֶה נִרְאֶה בַּמֵּעַיִם. וּכְשֶׁתָּמוּת יִדְבַּק בָּשָׂר בְּבָשָׂר וְיִתְכַּסֶּה חֵלֶב זֶה וְאֵינוֹ נִרְאֶה עַד שֶׁיִּתְפָּרֵק הַבָּשָׂר מִן הַבָּשָׂר. וְאַף עַל פִּי כֵן הֲרֵי זֶה אָסוּר. שֶׁאֵין זֶה חֵלֶב שֶׁהַבָּשָׂר חוֹפֶה אוֹתוֹ. וְכָל מָקוֹם שֶׁתִּמְצָא בּוֹ הַחֵלֶב תַּחַת הַבָּשָׂר וְהַבָּשָׂר מַקִּיף אוֹתוֹ מִכָּל סְבִיבָיו וְלֹא יֵרָאֶה עַד שֶׁיִּקָּרַע הַבָּשָׂר הֲרֵי זֶה מֻתָּר:
כסף משנה
8.
There are two cords of fat in the primary loin area, near the top of the thigh. While an animal is alive, this fat can be seen on the intestines.20For while an animal is alive, its meat hangs loosely (Chulin 93b). When, however, it dies, one portion of meat will cling to another and cover this fat. It will not be visible until the portions of meat will be separated from each other. Nevertheless, it is forbidden, because this is not fat that is covered by meat.21For in its lifetime, it is not covered by meat.
[In contrast,] wherever you find fat under meat, with the meat covering it and surrounding it in its entirety [so that] it will not be seen until the meat is cut away, it is permitted.

הלכה ט
חֵלֶב הַלֵּב וְחֵלֶב הַמֵּעַיִם וְהֵן הַדַּקִּין הַמְלֻפָּפִין כֻּלָּן מֻתָּרִין וַהֲרֵי הֵם כְּשֻׁמָּן שֶׁהוּא מֻתָּר. חוּץ מֵרֹאשׁ הַמְּעִי שֶׁסָּמוּךְ לַקֵּבָה שֶׁהוּא תְּחִלַּת בְּנֵי מֵעַיִם שֶׁצָּרִיךְ לִגְרֹר הַחֵלֶב שֶׁעָלָיו וְזֶהוּ חֵלֶב שֶׁעַל הַדַּקִּין שֶׁאָסוּר. וְיֵשׁ מִן הַגְּאוֹנִים שֶׁאוֹמֵר שֶׁרֹאשׁ הַמְּעִי שֶׁצָּרִיךְ לְגָרְרוֹ הוּא הַמְּעִי שֶׁיֵּצֵא בּוֹ הָרְעִי שֶׁהוּא סוֹף הַמֵּעַיִם:
כסף משנה
9.
The fat of the heart and the fat of all of the small intestines are permitted. They are considered like shuman which is permitted fat with the exception of the top of the intestine that is next to the maw and is the beginning of the small intestines. The fat must be scraped off it.22In his Kessef Mishneh, Rav Yosef Caro mentions that some interpret Chulin 93b as stating that a cubit of the intestines are forbidden and he quotes this view as halachah in the Shulchan Aruch (Yoreh De'ah 64:15). The Ramah, however, states that the forbidden measure is not a full cubit, but close to it. This is the fat of the small intestines that is forbidden. There are some of the Geonim who say that the top of the intestine from which the fat must be scraped off is the large intestine,23From the Rambam's statements in Hilchot Shechitah 6:10, it is obvious that he favors the first opinion. The Ra'avad differs and maintains that the second view should be followed. The Shulchan Aruch (Yoreh De'ah 64:15) states that one should follow the stringencies of both views. i.e., the colon from which feces are excreted which is the last of the digestive organs.

הלכה י
יֵשׁ בְּגוּף הַבְּהֵמָה חוּטִין וּקְרוּמוֹת שֶׁהֵן אֲסוּרִין. מֵהֶם מִשּׁוּם חֵלֶב וּמֵהֶן מִשּׁוּם דָּם. וְכָל חוּט אוֹ קְרוּם שֶׁאָסוּר מִשּׁוּם (ויקרא ג יז) (ויקרא ז כו) "כָּל דָּם לֹא תֹאכֵלוּ" צָרִיךְ לְנָטְלוֹ וְאַחַר כָּךְ יִמְלַח וִיבַשֵּׁל הַבָּשָׂר כְּמוֹ שֶׁאָמַרְנוּ. וְאִם חֲתָכוֹ וּמְלָחוֹ אֵינוֹ צָרִיךְ לְנָטְלוֹ. וְכֵן לְצָלִי (אֵינוֹ צָרִיךְ לְנָטְלוֹ). וְכָל חוּט אוֹ קְרוּם שֶׁהוּא אָסוּר מִשּׁוּם כָּל חֵלֶב בֵּין לְצָלִי בֵּין לְבִשּׁוּל צָרִיךְ לְנָטְלוֹ מִן הַבְּהֵמָה:
כסף משנה
10.
In the body of an animal, there are strands of tissue and membranes that are forbidden. Some are forbidden because of the prohibition against partaking of fat and others because of that against blood.24I.e., there is blood absorbed in the tissue or membrane. Whenever a strand of tissue or a membrane is forbidden because of the prohibition [Leviticus 3:17]: "Do not partake of any blood," one must remove it, and only then salt the meat as we explained.25The commentaries have cited Chapter 6, Halachot 10-12, as the Rambam's intent, but this point is not explicitly stated there. If one cut [the forbidden blood vessel], it does not have to be removed.26For the blood will flow out of it. Similarly, if one roasts [the meat], it does not have to be removed.27For the fire will cause the blood to drain off [see Shulchan Aruch (Yoreh De'ah 65:1)]. As the Maggid Mishneh mentions, there are some authorities who require that the blood vessels be cut open even when one roasts the meat.
Whenever a strand of tissue or membrane is forbidden because of the prohibition, "Do not partake of any fat," it must be removed from the animal whether one's intent is to cut it or roast it.28Otherwise, the fat will seep through the meat when it is being cooked or roasted.

הלכה יא
חֲמִשָּׁה חוּטִין יֵשׁ בַּכְּסָלִים. שְׁלֹשָׁה מִן הַיָּמִין וּשְׁנַיִם מִן הַשְּׂמֹאל. הַשְּׁלֹשָׁה שֶׁמִּן הַיָּמִין מִתְפַּצֵּל כָּל אֶחָד מֵהֶם לִשְׁנַיִם שְׁנַיִם. וְהַשְּׁנַיִם שֶׁמִּן הַשְּׂמֹאל מִתְפַּצְּלִין לִשְׁלֹשָׁה שְׁלֹשָׁה. וְכֻלָּן מִשּׁוּם חֵלֶב. וְחוּטֵי הַטְּחוֹל וְחוּטֵי הַכְּלָיוֹת מִשּׁוּם חֵלֶב. וְכֵן קְרוּם שֶׁעַל הַטְּחוֹל וּקְרוּם שֶׁעַל הַכְּסָלִים וּקְרוּם שֶׁעַל הַכְּלָיוֹת אֲסוּרִין מִשּׁוּם חֵלֶב. וּקְרוּם שֶׁעַל דַּד הַטְּחוֹל חַיָּבִין עָלָיו כָּרֵת. וּשְׁאָר הַקְּרוּם אָסוּר וְאֵין חַיָּבִין עָלָיו:
כסף משנה
11.
There are five strands of tissue in the flanks:29The Rama (Yoreh De'ah 64:13) explains that these strands of tissue extend from the lower portion of the backbone. As will be explained in the notes to Halachah 13, there are differences between his interpretation and that of the Rambam. three on the right and two on the left. Each of the three on the right splits into two and each of the two on the left splits into three. All are [forbidden] as fat.
The strands of tissue from the spleen and from the kidneys are forbidden as fat. Similarly, the membrane on the spleen, the membrane above the flanks, and the membrane on the kidneys are forbidden as fat. One is liable for kerat for the membrane on the thick side30Our translation follows the commentary of Rashi to Chullin 93a and the Shulchan Aruch (Yoreh De'ah 64:10). of the spleen. The remainder of the membrane is forbidden, but one is not liable for it.

הלכה יב
וּשְׁנֵי קְרוּמוֹת יֵשׁ לַכּוּלְיָא. הָעֶלְיוֹן חַיָּבִין עָלָיו כָּרֵת כַּחֵלֶב שֶׁעַל הַכּוּלְיָא. וְהַתַּחְתּוֹן הֲרֵי הוּא כִּשְׁאָר קְרוּמוֹת. וְחוּטִין שֶׁבָּהֶן אֲסוּרִין וְאֵין בָּהֶן כָּרֵת:
כסף משנה
12.
The kidney has two membranes. One is liable for kerat for [partaking of] the upper one as one is for [partaking of] the fat of the kidney itself. The lower one is like other membranes.31I.e., they are forbidden, but one is not liable for kerat for them. The strands of tissue in them are forbidden, but one is not liable for kerat for them.

הלכה יג
חוּטֵי הַלֵּב וְחוּטֵי הַיָּד וְחוּטֵי הָעֹקֶץ וְחוּטֵי הַלְּחִי הַתַּחְתּוֹן שֶׁבְּצַד הַלָּשׁוֹן מִיכָּן וּמִיכָּן. וְכֵן הַחוּטִין הַדַּקִּין שֶׁהֵן בְּתוֹךְ חֵלֶב הַדַּקִּין כְּמוֹ בֵּית עַכָּבִישׁ מְסֻבָּכִין זֶה בָּזֶה. וּקְרוּם שֶׁעַל הַמֹּחַ שֶׁבַּקֹּדְקֹד. וּקְרוּם שֶׁעַל הַבֵּיצִים. הַכּל אֲסוּרִין מִשּׁוּם דָּם:
כסף משנה
13.
The strands of tissue of the heart, of the foreleg, of the end of the spinal cord,32This follows the Rambam's interpretation of Chullin 93a. Rashi [and his view is cited by the Shulchan Aruch (Yoreh De'ah 64:13)] understands that passage as referred to the strands of fat mentioned in Halachah 11. of the lower jaw, those at either side of the tongue, and those within the fat of the small intestines which are interwoven like spiderwebs,33The Maggid Mishneh and Shulchan Aruch (Yoreh De'ah 75:3) write that in the present age, leniency is granted with regard to these blood vessels. Nevertheless, it is customary to remove them. and the membrane above the brain in the cranium and the membrane on the testicles are all forbidden because [of the prohibition against partaking] of blood.34I.e., these are blood vessels in which blood will be lodged after the slaughter of the animal. Therefore they must be removed or cut open (see Halachah 10) before the animal is cooked or roasted.

הלכה יד
בֵּיצֵי גְּדִי אוֹ טָלֶה שֶׁלֹּא הִשְׁלִים שְׁלֹשִׁים יוֹם מֻתָּר לְבַשְּׁלָן בְּלֹא קְלִיפָה. לְאַחַר שְׁלֹשִׁים יוֹם אִם נִרְאֶה בָּהֶן חוּטִין דַּקִּין אֲדֻמִּים בְּיָדוּעַ שֶׁהָלַךְ בָּהֶם הַדָּם וְלֹא יְבַשֵּׁל עַד שֶׁיִּקְלֹף אוֹ עַד שֶׁיֵּחָתֵךְ וְיִמָלַּח כְּמוֹ שֶׁבֵּאַרְנוּ. וְאִם עֲדַיִן לֹא נִרְאוּ בָּהֶן חוּטִין הָאֲדֻמִּים מֻתָּרִין:
כסף משנה
14.
When a kid or a lamb35The Maggid Mishneh notes that the Rambam (and his source, Chullin 93b) do not mention a calf when stating this leniency. Implied is that even at a younger age, the testicles of a calf are considered as developed. is less than 30 days old, it is permissible to cook its testicles without peeling [the membranes from them].36Until the kid or lamb reaches that age, the blood vessels are not developed and there is not a large quantity of blood flowing through them. After 30 days, if thin red lines can be seen within them, it is recognizable that blood has circulated through them and one should not cook [the testicles] until their outer membrane has been removed or until they have been cut open and salted, as we explained.37Chapter 6, Halachah 13. If thin red lines have not yet been seen within them, they are permitted.

הלכה טו
וְכָל בְּנֵי מֵעַיִם שֶׁהַמַּאֲכָל סוֹבֵב בַּחֲלָלָן אֵין מַחֲזִיקִין בָּהֶן דָּם:
כסף משנה
15.
We do not assume that there is blood in any of the digestive organs38This refers to the organs themselves. Hence they need not be salted (Maggid Mishneh, see Chapter 6, Halachah 18). With regard to the fat on these organs, it is possible for there to be blood vessels within them as mentioned above.
The Maggid Mishneh writes that we do assume that the stomach contains blood. This view is not, however, followed by the Shulchan Aruch (Yoreh De'ah 75:1). The Siftei Cohen 75:1 and the Turei Zahav 75:1, however, state that we do assume that the stomach of a fowl contains blood.
through which the food passes.

הלכה טז
יֵרָאֶה לִי שֶׁכָּל אֵלּוּ הַחוּטִין וְהַקְּרוּמוֹת אִסּוּרָן מִדִּבְרֵי סוֹפְרִים וְאִם תֹּאמַר שֶׁהֵן אֲסוּרִין מִן הַתּוֹרָה בִּכְלַל (ויקרא ג יז) "כָּל חֵלֶב וְכָל דָּם" אֵין לוֹקִין עֲלֵיהֶן אֶלָּא מַכַּת מַרְדּוּת וְיִהְיוּ כַּחֲצִי שִׁעוּר שֶׁהוּא אָסוּר מִן הַתּוֹרָה וְאֵין לוֹקִין עָלָיו:
כסף משנה
16.
It appears to me39This expression indicates a conclusion at which the Rambam arrived through his own powers of deduction without any explicit prior Rabbinic source. It appears that the Rambam did not arrive at a conclusive decision that the prohibition was of Rabbinic origin, but that he did favor this understanding. that all of these strands of tissue and membranes are forbidden according to Rabbinic Law. [Even] if one would say that they are forbidden according to Scriptural Law,40The verses mention kol, "any," fat or blood. That term could be understood as an inclusion beyond the ordinary scope of the term and hence, involving these substances as well. and are included in the prohibitions against partaking against any fat or any blood, one is not liable for lashes for them, only stripes for rebellious conduct. [Partaking of] them is comparable to partaking of half the measure of a forbidden substance. This is forbidden by Scriptural Law, yet one is not liable for lashes for it.41See Chapter 4, Halachah 16, Hilchot Shivitat Esor 2:3, et al.

הלכה יז
אֵין מוֹלְחִין חֲלָבִים עִם הַבָּשָׂר וְלֹא מְדִיחִין חֲלָבִים עִם בָּשָׂר. וְסַכִּין שֶׁחָתַךְ בָּהּ חֲלָבִים לֹא יַחְתֹּךְ בָּהּ בָּשָׂר. וּכְלִי שֶׁהֵדִיחַ בּוֹ חֲלָבִים לֹא יָדִיחַ בּוֹ בָּשָׂר. לְפִיכָךְ צָרִיךְ הַטַּבָּח לְהַתְקִין שָׁלֹשׁ סַכִּינִין. אַחַת שֶׁשּׁוֹחֵט בָּהּ. וְאַחַת שֶׁמְּחַתֵּךְ בָּהּ בָּשָׂר. וְאַחַת שֶׁמְּחַתֵּךְ בָּהּ חֲלָבִים:
כסף משנה
17.
We do not salt42For we fear that the meat will absorb some of the fat. or wash fat together with meat. One should not use a knife used to cut fat to cut meat, nor a container in which fats were washed to wash meat.43If one cleans the knife or the container first, scrubbing it carefully, it is permitted (Maggid Mishneh in the name of the Rashba).
Therefore a butcher should prepare three knives: one with which to slaughter, one to cut the meat,44For at the outset, the knife used to slaughter should not be used to cut meat (see Chapter 6, Halachah 20). and one to cut fat.

הלכה יח
וְאִם דֶּרֶךְ אוֹתוֹ מָקוֹם שֶׁיָּדִיחַ הַטַּבָּח הַבָּשָׂר בַּחֲנוּת. צָרִיךְ לְהַתְקִין לוֹ שְׁנֵי כֵּלִים שֶׁל מַיִם אֶחָד שֶׁמֵּדִיחַ בּוֹ בָּשָׂר וְאֶחָד שֶׁמֵּדִיחַ בּוֹ חֲלָבִים:
כסף משנה
18.
If it is local custom for the butcher to wash the meat in his store, he should prepare two containers of water, one in which to wash meat and one in which to wash fat.45The Chulin 8b asks: Why isn't one container sufficient? First he will wash the meat in it and then the fat? The text answers that perhaps he will forget and wash the fat first. In this instance, by contrast, since he has two clearly designated containers, he will not make such a mistake.

הלכה יט
וְאָסוּר לַטַּבָּח לִפְרשֹׁ חֵלֶב הַכְּסָלִים עַל הַבָּשָׂר כְּדֵי לְנָאוֹתוֹ. שֶׁהַקְּרוּם שֶׁעַל הַחֵלֶב דַּק וְיִתְמַעֵךְ בְּיַד הַטַּבָּח וְיָזוּב הַחֵלֶב וְיִבָּלַע בַּבָּשָׂר. וְכָל הַדְּבָרִים הָאֵלּוּ אָסוּר לַעֲשׂוֹתָן. וִאִם נַעֲשׂוּ לֹא נֵאֻסַר הַבָּשָׂר. וִאֵין מַכִּין אֶת הָעוֹשֶׂה אֶלָּא מְלַמְּדִין אוֹתוֹ שֶׁלֹּא יַעֲשֶׂה:
כסף משנה
19.
It is forbidden for a butcher to spread the fat of the flanks over the meat46The Maggid Mishneh mentions views that maintain that this restriction only applies directly after slaughter when the fat is still warm. Once it has cooled, it hardens. This ruling is quoted by the Shulchan Aruch (Yoreh De'ah 64:18). to make it appear attractive. [The rationale is that] the membrane over the fat is thin. It may become crushed by the butcher's hand and the fat will ooze out and saturate through the meat.
[Although] it is forbidden to perform all of these acts, if they are performed, the meat is not forbidden.47Although there are some more stringent views regarding certain particulars, the Rambam's view is cited by the Shulchan Aruch (Yoreh De'ah 64:19). Nor is the person who performs them given corporal punishment. Instead, he is taught not to act in this manner.

הלכה כ
וְכֵן אֵין מוֹלְחִין אֶת הַבָּשָׂר קֹדֶם שֶׁיָּסִיר מִמֶּנּוּ אֶת הַקְּרוּמוֹת וְאֶת הַחוּטִין הָאֲסוּרִין. וְאִם מָלַח מְסִירָם אַחַר שֶׁנִּמְלְחוּ. וַאֲפִלּוּ הָיָה בָּהֶן גִּיד הַנָּשֶׁה מְסִירוֹ אַחַר שֶׁנִּמְלַח וּמְבַשֵּׁל:
כסף משנה
20.
Meat should not be salted before the forbidden membranes and strands of tissue are removed.48This is a safeguard against the fat and blood being absorbed by the meat. If the meat was salted with them, they must be removed after the salting. Even if the gid hanesheh49See the following chapter. was among them, one may remove them after salting and cook [the meat].50According to the Rambam, after the fact, we do not say that the fat and/or blood was absorbed in the meat (see also Chapter 15, Halachah 32, and notes). The Rashba differs and maintains that one must remove the surface of the meat with them, because that surface also becomes forbidden. The Shulchan Aruch (Yoreh De'ah 64:20) quotes both views. The Rama also cites a more stringent perspective, but concludes that one may rely on the Rashba's view.

הלכה כא
וְטַבָּח שֶׁדַּרְכּוֹ לְנַקּוֹת הַבָּשָׂר וְנִמְצָא אַחֲרָיו חוּט אוֹ קְרוּם מְלַמְּדִין אוֹתוֹ וּמַזְהִירִין אוֹתוֹ שֶׁלֹּא יְזַלְזֵל בְּאִסּוּרִין. אֲבָל אִם נִמְצָא אַחֲרָיו חֵלֶב אִם הָיָה כִּשְׂעוֹרָה מַעֲבִירִין אוֹתוֹ. וְאִם נִמְצָא אַחֲרָיו כְּזַיִת חֵלֶב אֲפִלּוּ בִּמְקוֹמוֹת הַרְבֵּה מַכִּין אוֹתוֹ מַכַּת מַרְדּוּת וּמַעֲבִירִין אוֹתוֹ. מִפְּנֵי שֶׁהַטַּבָּח נֶאֱמָן עַל הַחֵלֶב:
כסף משנה
21.
When a butcher follows the practice of cleaning meat [from forbidden strands of tissue and membranes and] such a strand or membrane is found after he [alleged to have cleaned the meat], we teach him and warn him not to act negligently with regard to prohibitions.51He is not removed from his position, because these prohibitions are Rabbinic in origin (Maggid Mishneh). This ruling is, however, somewhat difficult to understand according to the second view mentioned in Halachah 16. [More stringent rules apply] if forbidden fat is found after he [alleged to have cleaned the meat]. If it is a barley corn in size, he is removed [from his position]. If an olive-sized portion of forbidden fat is found - even in several places - after he [alleged to have cleaned the meat], he is given stripes for rebellious conduct52For he transgresses the prohibition: "Do not place a stumbling block before the blind," which is interpreted as a charge forbidding one to cause others to transgress. Nevertheless, lashes are not given for the violation of this prohibition. and he is removed from his position. The rationale is that a butcher's word is relied upon with regard to fat.53And his customers might cook the meat without checking for fat (or being knowledgeable about the details of the prohibition). Hence, he would cause them to transgress.

קדושה הלכות מאכלות אסורות פרק ז
Kedushah Ma`akhalos Assuros Chapter 7