OTHER FORBIDDEN ACTIONS
Question: Things made on Shabbos should be forbidden! (They are abominations.)
Answer: "It (Shabbos) is Kodesh to you", but what is made on Shabbos is not Kodesh.
Suggestion: If one plowed with an ox and donkey together, or threshed with a muzzled ox, this should forbid (Rashi - the produce; Tosfos - the animals)!
Rejection: Melachah on Shabbos is a severe Isur, yet things made on Shabbos are permitted. Working with diverse species or with a muzzled animal is a less severe Isur, all the more it does not forbid!
Suggestion: If different species are planted together, the produce should be forbidden!
Rejection: It says regarding Kil'ai ha'Kerem (different species planted in a vineyard or with grapes), "Tukdash." We read this "Tukad Esh" (the produce will be burned);
Inference: Kil'ai Zera'im (different species planted together without grapes) are permitted.
Suggestion: Perhaps we infer that one may benefit from Kil'ai Zera'im, but one may not eat them!
Rejection: They are equated to (offspring of) Kil'ai Behemah (crossbred animals) - "Behemtecha Lo Sarbi'a Kil'ayim Sadcha Lo Sizra Kil'ayim";
Just like one may eat Kil'ai Behemah, also Kil'ai Zera'im.
Question: What is the source to permit Kil'ai Behemah?
Answer: The Torah forbids Kil'ai Behemah to the Mizbe'ach. We infer that they are permitted to people.
Suggestion: If Oso v'Es Beno are slaughtered on the same day, the latter should be forbidden! (It was slaughtered b'Isur.)
Rejection: The Torah forbids Mechusar Zeman (something that may not be offered yet) to the Mizbe'ach (this includes Oso v'Es Beno, which may not be slaughtered yet). We infer that it is permitted to people.
Suggestion: If one took Em Al ha'Banim (a mother bird resting on its eggs or chicks), the mother should be forbidden!
Rejection: The Torah commands to send away the mother. (One who finds it has no reason to suspect that it is forbidden. He may eat it.) The Torah would not cause a guiltless person to sin.
BENEFIT FROM BASAR V'CHALAV
Question (Reish Lakish): What is the source to forbid meat cooked with milk?
Answer #1 (Reish Lakish): Regarding Korban Pesach, it says "Al Tochlu Mimenu Na u'Vashel Mevushal." The repetition teaches that something else cooked is forbidden (like Pesach that was cooked), i.e. Basar v'Chalav.
Question (and Answer #2 - R. Yochanan): Why don't you learn like Rebbi?
(Rebbi): "Do not eat it" is extra (other verses forbid blood). It forbids eating Basar v'Chalav.
Question: Perhaps it forbids something else!
Answer: We learn from the context. The verse discusses two kinds (Tosfos - deer and wild goat; Rashi - a blemished Korban that was redeemed, in some ways it is like Chulin, in some ways it is like Kodshim), so it comes to forbid two kinds.
Answer (Reish Lakish): Rebbi teaches the Isur to eat. I gave the source to forbid benefit. (Basar v'Chalav is equated to a Pesach that was cooked. Since one may not eat it, it is Asur b'Hana'ah.)
Question: How does Rebbi learn that benefit is forbidden?
Answer: (He learns from a Gezeirah Shavah "Kodesh-Kodesh.") The verse (in Devarim) forbidding Basar v'Chalav begins "you are a Kodesh nation to Hash-m", similar to "there will not be Kadesh in Bnei Yisrael" (a man who cannot be Mekadesh a woman, i.e. a slave, may not have relations with a Bas Yisrael. Alternatively, a man may not wantonly have relations (Rashi - Mishkav Zachar));
Just like Kadesh is an Isur of (relations, which is) Hana'ah, also Basar v'Chalav.
Answer #3 (d'Vei R. Eliezer - Beraisa): It says "do not eat any Nevelah (... you may sell it to a Nochri) Lo Sevashel Gedi ba'Chalev Imo" - when you sell a Nevelah to a Nochri, you may not cook it (beforehand in milk, for this would forbid benefit from it).
Answer #4 (Tana d'Vei R. Yishmael): Three verses say "Lo Sevashel Gedi ba'Chalev Imo." They forbid eating, benefit and cooking.
Answer #5 (Beraisa - Isi ben Yehudah): One verse forbidding Basar v'Chalav says "you are a Kodesh nation to Hash-m", similar to "you will be Kodesh people to Me. Do not eat Terefah meat in the field";
Just like Terefah may not be eaten, also Basar v'Chalav.
A Kal va'Chomer forbids benefit;
Orlah did not result from a sin, yet it is Asur b'Hana'ah. Basar v'Chalav results from a transgression, all the more so it is Asur b'Hana'ah!
Question: We cannot learn from Orlah, for it never was permitted!
Answer: Chametz (during Pesach) shows that Isur Hana'ah does not depend on this. It is Asur b'Hana'ah, even though it was once permitted!
Question: We cannot learn from Chametz, for one who eats it (b'Mezid) gets Kares!
Answer: Kil'ai ha'Kerem shows that Isur Hana'ah does not depend on this. (It is Asur b'Hana'ah, even though it is only a Lav.)
QUESTIONS ON THE KAL VA'CHOMER
Question: Why did the Tana need a Gezerah Shavah to forbid eating Basar v'Chalav? Also this can be learned from the Kal va'Chomer!
Orlah did not result from a sin, yet one may not eat or benefit from it. Basar v'Chalav results from a transgression, all the more so one may not eat or benefit from it!
Answer: The Kal va'Chomer can be refuted;
One may not plow with Kilayim (different species of animals), or with a muzzled animal, yet if one did, nothing is forbidden to eat.
(Now that a Gezerah Shavah forbids eating Basar v'Chalav, we cannot refute the Kal va'Chomer like this (regarding benefit), for Basar v'Chalav may not be eaten, whereas forbidden plowing does not forbid anything to be eaten.)
Question: Why did the Tana use Kil'ai ha'Kerem to show that Isur Hana'ah does not depend on Kares? We can learn this from Orlah itself, and learn Basar v'Chalav from the Tzad ha'Shavah of Orlah and Chametz!
Answer #1 (Rav Ashi): If we learned from the Tzad ha'Shavah, Nevelah would refute the Kal va'Chomer. It is Asur to eat, but it is Mutar b'Hana'ah!
Objection (Rav Mordechai citing Reish Lakish): We challenge a Tzad ha'Shavah only from laws of the sources we learn from (not found in the Lamed (what we want to learn)). We do not challenge it from elsewhere (other matters that share the properties of the sources (here, one may not eat them), but do not have the property we want to).
Question (Rav Ashi): How do you answer (Question (c))? We should learn from the Tzad ha'Shavah (of Orlah and Chametz)!
Answer (Rav Mordechai): We could challenge it. Both Orlah and Chametz grow from the ground, but Basar v'Chalav does not.
Question (Rav Ashi): Even now that we learn also from Kil'ai ha'Kerem, that challenge remains, for also Kilayim grows from the ground!
Answer (Rav Mordechai): We can challenge a Tzad ha'Shavah from anything (common to the sources, but not in the Lamed, even if it is not a leniency or stringency, i.e. there is no reason why it should affect the law);
Here, we may not challenge that Kilayim grows from the ground, unlike Basar v'Chalav, for this is not a leniency or stringency.
Question (Rav Ashi): The Tana does not learn from Kilayim alone, rather from all three. It is like a Tzad ha'Shavah. We can challenge it. All the sources (Orlah, Chametz and Kilayim), grow from the ground, unlike Basar v'Chalav!