1) USING A KNIFE OF AVODAH ZARAH FOR "SHECHITAH"
QUESTION: Rav Nachman in the name of Rabah bar Avuha says that one is permitted to slaughter an animal with a knife that was used for Avodah Zarah, but one may not cut meat with such a knife. One is permitted to slaughter an animal with a knife of Avodah Zarah, because it is not considered as though one is benefiting from the knife. Since a live animal is worth much more than a dead animal (since a live animal can be used for breeding, plowing, and milking), one is not considered to be deriving benefit from the knife by using it to slaughter the animal. One is forbidden to cut meat with such a knife, because by cutting up the meat one derives benefit from the knife of Avodah Zarah, since the meat is not fit to eat until it is cut.
The Gemara asks that one should be forbidden to cut or slaughter with a knife used for Avodah Zarah because of the oily residue left on the knife from the Nochri's animal. The Gemara answers that Rav Nachman's ruling applies only to a new knife that was not yet used to slaughter animals for Avodah Zarah, but that was used only to cut wood for Avodah Zarah. Alternatively, his ruling applies to a knife that was used to slaughter animals for Avodah Zarah, but the knife underwent the proper purging procedure to remove any trace of Neveilah.
The ruling of Rav Nachman still seems difficult. The Torah commands, "You shall completely destroy all of the places where the nations which you shall possess served their gods, upon the high mountains, and upon the hills, and under every leafy tree" (Devarim 12:2). The Gemara in Avodah Zarah (51b) explains that this verse refers to utensils that were used in the service of Avodah Zarah, since there is another verse (Shemos 34:13) that commands us to destroy the idols themselves. Since one is obligated to destroy the utensils used for Avodah Zarah, and keeping such utensils in one's home is forbidden, how can one be permitted to use such a knife, l'Chatchilah, to slaughter an animal?
(a) The PNEI YEHOSHUA initially suggests that the knife of Avodah Zarah which Rav Nachman permits to be used for Shechitah does not belong to a Jew. Rather, the Jew is borrowing it from a Nochri, and thus there is no obligation for the Jew to destroy it.
The Pnei Yehoshua rejects this answer, because there is another problem that this answer does not resolve. The Torah prohibits not only maintaining utensils of Avodah Zarah, but it also prohibits wanting such utensils to exist ("Rotzeh b'Kiyumo"; see Avodah Zarah 63b). Although the Jew does not own the knife, he wants it to exist and not to be destroyed, because if it is lost or stolen he will be obligated to pay its value to the Nochri.
(b) Therefore, the Pnei Yehoshua gives another answer based on the opinion of RABEINU ELAZAR of MITZ cited by the TUR (YD 146:2). Although the Halachah is that an object of Avodah Zarah that belongs to a Jew can never be nullified (even by a Nochri), Rabeinu Elazar rules that this applies only to the actual object that was worshipped. Utensils that were used only for the service of Avodah Zarah can be nullified by a Nochri (by declaring that these utensils will no longer be used for Avodah Zarah; see Avodah Zarah 43a, where the Gemara says that a Nochri may even be forced to nullify them), even when a Jew owns them. Accordingly, Rav Nachman is referring to a Jew who found a knife used for Avodah Zarah, or who obtained it in some other way. He did not intend to acquire ownership of the knife, but rather he waited to find a Nochri to be Mevatel it. If he would fail to find a Nochri to be Mevatel it, then he would destroy it himself. Since he looks for a way to be Mevatel the knife's designation for Avodah Zarah or to for a way to destroy the knife, he does not want it to exist and he does not transgress any of the Torah's requirements to destroy objects of Avodah Zarah.
The CHIDUSHEI CHASAM SOFER in Avodah Zarah (32a, DH uv'Maseches) cites support for the Pnei Yehoshua's answer from the Gemara in Avodah Zarah (53b). The Gemara there discusses the Torah's commandment (Devarim 12:3) to burn the Asheirah trees that the Jewish people found when they entered Eretz Yisrael. The Gemara asks that since Eretz Yisrael was the inheritance of Avraham Avinu, how could the nations who inhabited the land after Avraham Avinu cause the trees to become forbidden by worshipping them? There is a rule that a person cannot cause an object that does not belong to him to become forbidden! Even if the Torah refers to the Asheirah trees that were worshipped before the time of Avraham and indeed became forbidden, it should suffice to force a Nochri to be Mevatel them (see RASHI there, DH Michdei). That is the Gemara's question in Avodah Zarah.
The Chasam Sofer questions the Gemara's question there. Why does the Gemara ask that the Jewish people should have had a Nochri be Mevatel the Avodah Zarah right away when they entered Eretz Yisrael? It would have taken them some time to find a Nochri from the time they entered until the time that they conquered Yericho. How could they have been permitted to let the Asheirah trees remain in their possession during that time? It must be, as the Pnei Yehoshua writes, that one who keeps Avodah Zarah in his possession with intent to have a Nochri nullify it at the earliest possible opportunity does not transgress the prohibition against owning Avodah Zarah or wanting it to exist. (See, however, the Chasam Sofer there, who later questions this proof for the Pnei Yehoshua.) (D. BLOOM)
2) "SHECHITAH" PERFORMED WITH A PROHIBITED KNIFE
QUESTION: Rav Nachman in the name of Rabah bar Avuha says that one is permitted to slaughter an animal with a knife that was used for Avodah Zarah, but one may not cut meat with such a knife. One is permitted to slaughter an animal with a knife of Avodah Zarah, because it is not considered as though one is benefiting from the knife. Since a live animal is worth much more than a dead animal (since a live animal can be used for breeding, plowing, and milking), one is not considered to be deriving benefit from the knife by using it to slaughter the animal.
The Gemara says that if the animal is mortally ill, then slaughtering is considered a benefit to the owner, since he will be gaining edible eat instead of being left with a useless Neveilah. Since one thereby benefits from the knife, he may not slaughter such an animal with a knife of Avodah Zarah.
What is the Halachah when, b'Di'eved, a person slaughtered an ill animal with a knife of Avodah Zarah?
The SHACH (YD 10:1) rules that the animal is permitted to be eaten, but its value should be thrown into the sea in order to avoid deriving benefit from the knife of Avodah Zarah.
Why is the Shechitah valid? There is a rule that "Iy Avid Lo Mehani" -- if one performs an act that the Torah prohibits, the act does not take effect. Accordingly, Shechitah performed with a knife of Avodah Zarah should be invalid, since the Torah prohibits such an act.
(a) REBBI AKIVA EIGER (Chidushim, Ma'arachah 11) explains that the rule of "Iy Avid Lo Mehani" applies only to cases in which the Torah prohibits a specific act (such as the prohibition against a Kohen marrying a Gerushah). The Torah does not give legal efficacy to an act that it proscribes. That is part of the specific Isur of the Torah. In the case of benefiting from an object of Isurei Hana'ah, such as a knife used for Avodah Zarah, the Torah does not discuss the specific act, but rather it gives a general prohibition. In such a case, the rule of "Iy Avid Lo Mehani" does not apply. (Rebbi Akiva Eiger uses this approach to explain why a contract of Kidushin that a man writes on an object that is Asur b'Hana'ah and gives to a woman constitutes a valid Kidushin. In that case, too, there is no specific Isur in the Torah against writing a Shtar Kidushin on an object that is Asur b'Hana'ah; it is only a general prohibition not to benefit from Isurei Hana'ah.) (Z. Wainstein)
(b) The SHACH (CM 208:2) writes that this rule (that when one does an act prohibited by the Torah, the act is not effective) applies only to cases in which it is not possible to bring about the desired effect in any way other than through the prohibited act. The Isur of Temurah is one example. The only way one can exchange a sanctified animal for another animal is through an Isur; there is no permissible way to exchange a sanctified animal for another animal. In contrast, when one slaughters an ill animal with a knife of Avodah Zarah, since it is possible to perform the Shechitah in a permissible manner (such as by using a permitted knife), the rule of "Iy Avid Lo Mehani" does not apply.
(c) RAV ELCHANAN WASSERMAN Hy'd in KOVETZ HE'OROS (76:3-4) writes that the Halachic result caused by an act that a person performs can take effect in one of two ways. First, the Halachic effect can be accomplished by the person himself, such as in the cases of Kinyanim, Kidushin, and Gerushin, where the person's intention causes a certain Halachic status to take effect. Second, the Halachic effect can occur through the action alone, independent of the person's intention, such as in the case of Shechitah, where it is the act of Shechitah that permits the animal to be eaten. Although in such a case it is necessary that a person perform the action ("Ko'ach Gavra"), it is not the person who is permitting the meat but it is the Shechitah which is permitting the meat (the requirement that it be done by a person is only a condition in the Matir of Shechitah).
Accordingly, the principle of "Iy Avid Lo Mehani" does not apply to Shechitah, because this principle applies only where the Halachic status comes about through the person himself. When the person sinned, the Halachic status that he otherwise would have caused to take effect does not take effect. With regard to Shechitah, the change in Halachic status (the meat becoming permitted) occurs as a result of the act of Shechitah itself and is not related to the person's will or intent. The independent act of Shechitah causes the meat to become permitted, and even though the person did an Aveirah while doing the Shechitah, it is not the person making the meat permitted, and therefore the Shechitah remains valid. (See also Insights to Bava Kama 70:2 and 71:2.)
3) THE FORBIDDEN SUBSTANCE ABSORBED IN A KNIFE USED FOR AVODAH ZARAH
QUESTION: Rav Nachman in the name of Rabah bar Avuha says that one is permitted to slaughter an animal with a knife that was used for Avodah Zarah, but one may not cut meat with such a knife.
The Gemara asks that one should be forbidden to slaughter an animal with a knife used for Avodah Zarah because of the oily residue left on the knife from the Nochri's animal. RASHI (DH v'Teipuk Lei) explains that this refers to the fats of the Neveilos that the Nochri slaughtered.
Since the Gemara is discussing a knife that was used for Avodah Zarah, why does Rashi explain that the Gemara is discussing the fats of Neveilah? He should explain that the Gemara is discussing the more severe problem of the fats of animals that were offered for Avodah Zarah! (The Isur of Avodah Zarah includes an Isur Hana'ah, while the Isur of Neveilah does not.) (RASHASH)
ANSWER: The RASHASH explains that Rashi's intention is to point out the strength of the Gemara's question. Even if the knife had not yet been used for an animal that was sacrificed for Avodah Zarah, it still should be prohibited because of the Isur of Neveilah absorbed in it. (Z. Wainstein)
4) WHEN IS "LIBUN" NECESSARY FOR KNIVES USED WITH FORBIDDEN SUBSTANCES
QUESTION: The Gemara says that one may perform Shechitah with a knife used for Avodah Zarah when the knife underwent the process of Libun. Libun entails "whitening" the utensil with the heat of a flame so that the prohibited substance is expelled from the utensil.
Why is Libun necessary? The Gemara in Avodah Zarah (75b) teaches that a knife needs only Ne'itzah (imbedding the knife in the ground ten times) to remove the prohibited substance, and it does not need Libun. Even if the Gemara there intends only to permit the knife for cutting cold foods, while the Gemara here is giving a way to permit the knife to be used even if the Beis ha'Shechitah is hot, Libun still should not be necessary. The Gemara in Pesachim (30b) teaches that Hag'alah suffices for a knife, even to use the knife to cut a hot object! (TOSFOS 8a, DH she'Livnah)
(a) TOSFOS answers in the name of RABEINU TAM that when the Gemara in Pesachim says that Hag'alah suffices to remove Chametz that is absorbed in the knife, it refers specifically to a substance that was permitted when it became absorbed in the knife and only later became prohibited (when Pesach arrived). In such a case, Hag'alah suffices. When, however, the absorbed substance was forbidden at the time that it became absorbed in the knife, Libun is required.
(This answer is not followed in practice. The SHULCHAN ARUCH and REMA (OC 451:4) write that the custom is to be stringent with regard to Chametz and not to consider Chametz a food that was permitted at the time of contact with the utensil.)
(b) Rabeinu Tam answers further that the Gemara in Pesachim refers to small knives that are not used over the fire. The Gemara here refers to large knives that are often used to hold the meat as it roasts over the fire. Since these knives were used over the fire, they require Libun.
This answer is supported by the wording of the Tosefta, which lists knives together with "spits" and "grills" when it says that Libun is required, implying that the knives, like spits and grills, were used over the fire.
(This answer is also not followed in practice. The Shulchan Aruch (YD 121:7) writes that if one intends to use the utensils for hot foods, he must perform Libun.)
(c) TOSFOS in Avodah Zarah (76b, DH Amar) cites RABEINU ELCHANAN who answers that the Gemara here refers to large knives that tend to have indentations and small cavities. The forbidden substance adheres to the inside of the indentations. Hag'alah works only to remove the taste of the substance that is absorbed in the utensil itself; it does not work to remove the actual, oily substance on the surface of the utensil. Although Ne'itzah serves to remove the oily substance from the surface of the utensil, it does not reach the inside of the indentations, and thus the forbidden substance remains. Therefore, Libun is necessary. In contrast, the Gemara in Pesachim refers to small knives that have no indentations in them. (Z. Wainstein)
5) PEELING AWAY THE MEAT "KEDEI KELIPAH"
QUESTION: The Gemara records a dispute between Rav and Rabah bar bar Chanah in the case of one who slaughtered an animal with the knife of a Nochri. Rav states that one must peel away the outer layer ("Kedei Kelipah") of the neck ("Beis ha'Shechitah") where the Shechitah was performed and discard it. Rabah bar bar Chanah maintains that it suffices to rinse that area with water. Rav requires that the area be peeled away because the pressure applied by the knife ("Duchka d'Sakina") causes the prohibited fats (RASHI) on the knife to be absorbed into the animal.
However, the Gemara later (97a) teaches that fat that became absorbed in a piece of meat spreads throughout the entire piece of meat. Why, then, does it suffice to peel away merely the outer layer?
Moreover, the animal should be permitted without the need to peel off any amount of the flesh, even if prohibited fats became absorbed in it. The animal is much larger than the knife, and thus whatever fat entered the animal from the knife should become Batel. (RASHBA)
(a) The RASHBA answers that the Beis ha'Shechitah is not hot enough for the fat to spread all the way through the animal, but it is warm enough to enable the fat to prohibit "Kedei Kelipah." (See also ME'IRI.)
Accordingly, since the forbidden fat enters only the outer layer of the animal's flesh, it is only that layer which can be Mevatel the Isur, but that layer is not significantly larger than the knife.
(b) Fat absorbed in a knife is not as oily as regular fat, and thus it can spread only "Kedei Kelipah."
(c) The fat indeed does spread throughout the entire animal, and it should become Batel. However, since one knows the exact location at which the initial contact of the knife with the flesh occurred, he is required to act stringently and to peel "Kedei Kelipah" from that area.
6) HALACHAH: FOOD CUT WITH A COLD KNIFE OF "ISUR"
OPINIONS: The Gemara records a dispute between Rav and Rabah bar bar Chanah in the case of one who slaughtered an animal with the knife of a Nochri. Rav states that one must peel away the outer layer ("Kedei Kelipah") of the neck ("Beis ha'Shechitah") where the Shechitah was performed and discard it. Rabah bar bar Chanah maintains that it suffices to rinse that area with water. The Gemara (in the second version of its explanation) explains the dispute. Both Amora'im agree that the Beis ha'Shechitah is considered "cold," and, therefore, the forbidden food ("Isur") is not absorbed into the animal itself. Rabah bar bar Chanah requires that the area be rinsed in order to remove any Isur that was transferred from the surface of the knife to the neck of the animal. Rav requires that the area be peeled away, because the pressure applied by the knife ("Duchka d'Sakina") causes the Isur on the knife to be absorbed into the animal, but it does not reach further than the level which can be removed by peeling.
The Gemara does not decide conclusively in favor of either opinion. RASHI (DH Duchka) writes that since this case involves a Torah prohibition, one must act stringently and peel away the area around the Beis ha'Shechitah. L'Chatchilah, of course, one may not use a knife of a Nochri for Shechitah. The discussion of the Gemara applies only b'Di'eved, once such a knife was already used.
Does the principle of "Duchka d'Sakina" apply whenever a knife (that may have absorbed the taste of a forbidden food) is used, or only under certain conditions?
(a) TOSFOS (DH Agav) cites RABEINU YITZCHAK BEN MEIR who rules that every time the forbidden fats are removed from an animal after it is slaughtered, it is necessary to peel off a layer of meat from all parts of the animal which the knife touched. This is because the knife became smeared with the forbidden fats, which then became absorbed into the other parts of the meat where the knife cut. Rabeinu Yitzchak's source is the Gemara here which teaches that the "Duchka d'Sakina" causes the Isur to become absorbed into the meat.
(b) Tosfos states that the practice today is not to require the peeling of the meat after the forbidden fats have been removed. The removal of the forbidden fats is not comparable to the case of the Gemara, because perhaps "Duchka d'Sakina" causes Isur to become absorbed only because the Beis ha'Shechitah is warm. (When the Gemara says that the Beis ha'Shechitah is "cold," it does not mean that it is entirely cold. Rather, it means that it is not hot, but it is warm. See RASHBA and ME'IRI.) In contrast, "Duchka d'Sakina" cannot cause Isur to become absorbed in the rest of the meat, which is cold.
Tosfos cites support for this distinction from the continuation of the Gemara. The Gemara asks why is it not necessary to Kasher a Kosher knife after every act of Shechitah? The knife should become Asur by absorbing the taste of "Ever Min ha'Chai" through "Duchka d'Sakina" during the act of Shechitah! The Gemara answers that the knife absorbs from the animal only when the animal is warm, and it is warm only at the end of the act of Shechitah, but by that time the animal is no longer forbidden as "Ever Min ha'Chai." Thus, no Isur enters the knife. This implies that "Duchka d'Sakina" does not cause an Isur to become absorbed when the food is cold.
Tosfos cites another proof for the distinction between a warm surface and a cold surface with regard to "Duchka d'Sakina" from the Gemara later (111b). The Gemara states that a radish that was cut with a knife used for meat may not be eaten with milk, because a radish is a "sharp" food ("Davar Charif") and it absorbs the taste of the meat from the knife. Tosfos infers from there that the radish absorbs only because of its sharpness, but not because of the "Duchka d'Sakina." The pressure of the knife is not powerful enough to cause the taste of the meat to become absorbed into cold food.
(c) However, other opinions maintain that the pressure of the knife is able to draw out Isur even from cold food. The BEIS YOSEF (end of YD 89) cites the ORCHOS CHAYIM in the name of the BA'AL HA'TERUMAH, who writes that RABEINU SHIMSHON permitted eating cheese with bread that was cut with a knife used for meat. He says that the reason is that this is "Nosen Ta'am Bar Nosen Ta'am d'Heteira" (the meat gave its taste to the knife, and the knife gave its taste to the bread, and thus the taste of the meat in the bread is two stages removed from its source; see SHULCHAN ARUCH YD 95:1), which is Mutar. (See also BACH there, and PRI MEGADIM in MISHBETZOS ZAHAV YD 96:3.) (D. BLOOM)