WHY WE MAY NOT RENT TO KUSIM
Question: Why is it permitted to rent to Nochrim?
Answer: We tell him not to work on Shabbos, and he complies.
Question: Likewise, it should be permitted to rent to Kusim. We will tell him not to work on Chol ha'Moed!
Answer: The Kusi will not listen. He thinks that he knows the law better than we do.
Question: R. Shimon ben Elazar forbade because people call it the Yisrael's field. Even without this, it is forbidden due to "Lifnei Iver"!
Answer: Indeed, the Tana means that it is forbidden due to Lifnei Iver, and also because people call it the Yisrael's field.
PARTNERSHIP WITH NOCHRIM
Version #1: Some Yisraelim and Nochrim were joint sharecroppers (in saffron gardens). The Nochrim would work on Shabbos, and the Yisraelim the next day. Rava permitted it.
Question (Ravina - Beraisa): If a Yisrael and Nochri accepted to work a field as sharecroppers, the Yisrael may not tell the Nochri 'take your share of the Peros for working on Shabbos, and I will take a corresponding (extra) share during the week';
If they stipulated from the beginning, it is permitted;
If they made a calculation (of how much each should get), it is forbidden.
Rava was embarrassed (that he erred). Later, it was found that they had stipulated from the beginning (the ruling was correct).
Version #2 (Rav Gavihah of Bei Kesil): Some Yisraelim and Nochrim were hired together to plant new trees. The Yisraelim told the Nochrim to work the trees (and enjoy the Peros) for the three years of Orlah, and the Yisraelim would work them for three other years. Rava permitted it. (end of Version #2)
Question: Version #2 cannot be correct, for then Ravina had no question from the Beraisa!
Answer: Indeed, Ravina brought the Beraisa to support Rava (if they stipulated from the beginning, it is permitted, for the Nochri is not like the Yisrael's worker, even though the Yisrael profits. The same applies here!)
Question: Rava was embarrassed! (Surely, Ravina asked against him.)
Answer: According to Version #2, Rava was not embarrassed.
Question: May they divide the money equally without mentioning the share for Shabbos?
Answer (Beraisa): If they stipulated from the beginning, it is permitted;
Inference: If they did not stipulate from the beginning, it is forbidden.
Question: We may infer the opposite from the Seifa!
(Seifa): If they made a calculation, it is forbidden.
Inference: If they did not made a calculation, it is permitted!
Conclusion: The inferences contradict one another. We cannot determine which is correct.
NOCHRIM ARE SUSPECTED OF BESTIALITY
(Mishnah): We may not leave animals in inns owned by Nochrim, for they are suspected of bestiality;
A woman may not be secluded with Nochrim, for they are suspected of illicit relations;
A man may not be secluded with Nochrim, for they are suspected of murder.
(Gemara - Beraisa) Contradiction: We may buy an animal from Nochrim for a Korban. We are not concerned lest it was Bo'el (played the male part in relations) a Nochri, or a Nochri was Bo'el it, or it was Muktzeh (designated for idolatry; Tosfos - and given to the priests and fed fodder of idolatry), or was worshipped.
Granted, we are not concerned for Muktzeh, or that it was worshipped, for a Nochri would not sell such an animal.
However, we should be concerned for bestiality!
Answer #1 (Rav Tachlifa): A Nochri does not sleep with his animal, for this would make it sterile. (Other answers will be given on 23a.)
Question: This does not apply to male animals!
Answer (Rav Kahana): A Nochri does not sleep with his male animal, for this would make it weaker.
Question (Beraisa): We may buy an animal from a Nochri's shepherd (a Nochri) for a Korban.
We should be concerned lest the shepherd slept with it (it is not his animal)!
Answer: He is afraid lest the owner find out and deduct from his wages.
Question (Beraisa): We may not give an animal to a Nochri shepherd.
We should not be concerned. He is afraid to sleep with it lest he lose his wages!
Answer: A shepherd of a Nochri fears his boss. Since all Nochrim enjoy bestiality, they suspect each other;
A shepherd of a Yisrael thinks that his boss does not suspect him.
(Rabah): Lowly people understand and fear each other.
Question: Why may we buy a male animal from a Nochris? Perhaps she slept with it! (The deterrents of sterility and weakening the animal do not apply.)
Answer: She is afraid lest the animal follow her around (and people will know why).
Question: Rav Yosef taught that a widow may not keep a dog, nor host a Talmid in her inn.
Granted, she is suspected of sinning with the Talmid. She trusts that he will not reveal anything.
However, why are we concerned for a dog? It would follow her around!
Answer: People will assume that it follows her because she often feeds it meat.
Question: Why may we not leave a female animal with a Nochris?
Answer #1 (Mar Ukva bar Chama): Nochrim often go to other women. Perhaps a Nochri will come, and not find her, and have relations with the animal.
Answer #2: Even if the Nochri finds her, perhaps he will prefer to have relations with the animal;
Nochrim prefer animals of Yisrael above their own wives.
(R. Yochanan): When the serpent had relations with Chavah, he inserted filth in her (which passed to her seed).
Question: Also Yisrael descends from Chavah!
Answer: When Yisrael came to Sinai, the filth left them. It never left the Nochrim.
Question: Are we concerned lest Nochrim have bestiality with birds?
Answer: Yes.
(Rav Yehudah citing R. Chanina): I saw a Nochri buy a duck, have relations with it, choke it, roast it and eat it.
(R. Yirmeyah mi'Difti): I saw an Aravi buy a thigh of meat, cut a hole (for relations), have relations with it, roast it and eat it.