(Beraisa): "V'Samti Lecha Makom" - teaches that there will be a place of refuge in your (Moshe's) lifetime, in your place (Machaneh Levi).

In the Midbar, Shogeg murderers went to Machaneh Levi. A Levi would be exiled to a different neighborhood in Machaneh Levi. If he was exiled to a different part of his own neighborhood, he received refuge.

(Rav Acha brei d'Rav Ika): "Ki v'Ir Miklato Yeshev" includes (even) the city that already absorbed him (he was already living there.)

Yevamos 41a (Mishnah): No woman may get engaged or married for three months after she was divorced or widowed. (This is for Havchanah, i.e. to know who fathered her children. If she remarries after three months, surely children born within six months are from her previous husband, and children after that are from her new husband.)

37a - Question (Rav Ashi): If a Kohen married a woman pregnant from or nursing a baby from another man, did we enact a leniency for him (that he need not divorce, so he may keep her after she finishes nursing)?

Answer (R. Hoshaya brei d'Rav Idi): No. If a Kohen married a Safek Yavamah (her son died within 30 days), since he cannot keep her if she does Chalitzah, we rely on Chachamim (who hold that the baby was viable, even though R. Shimon ben Gamliel argues);

Here, there is no opinion to rely on! All hold that he must divorce her!

Rav Acha and Rafram argued about one who was Mekadesh a woman within three months, and fled.

Opinion #1: We put him in Niduy (until he divorces her);

Opinion #2: It suffices that he fled.

A case occurred, and Rafram ruled that it suffices that he fled.

Rambam (Hilchos Gerushin 11:24): If one was Mekadesh within 90 days, we excommunicate him. If he made Nisu'in within 90 days, we separate them until after 90 days, and he remains with his wife.

Ra'avad: We excommunicate him until he divorces. If Niduy were only until he separates, why did the Gemara say that if he fled, this suffices? Even if he did not flee, separation suffices! Rather, we force him to divorce, unless he fled. However, if he made Nisu'in, he must divorce her.

Magid Mishneh and Nimukei Yosef (Yevamos 11a DH Itmar): The Rambam connotes that Niduy is for transgressing a mid'Rabanan law, but we do not force him to divorce, even if he made Nisu'in. We separate him, and if he fled, this exempts him from Niduy.

Beis Yosef (EH 13 DH u'Mah she'Chosav v'Im): One need not say like the Ra'avad. Some explain like him. Teshuvas ha'Ran (58) is like the Rambam. This is a mid'Rabanan law, so one may rely on the Rambam and the Ran.

Rosh (Yevamos 4:6): Rashi said that since he fled, this shows that he does not want to make Nisu'in within the time. This connotes that l'Chatchilah we tell him to flee. R. Yechi'el of Paris ruled like this. It seems that he must flee so far that he cannot return within the three months. It is unreasonable that one may be Mekadesh here and flee to another city. If so, Chachamim's enactment is Batel!

Rebuttal (Bedek ha'Bayis DH v'Ein): Even if one may be Mekadesh and flee, the enactment is not Batel. It is a big pain to leave one's job and city and flee to another city. The other Poskim did not specify. This connotes they do not require fleeing so far.

Rosh (Teshuvah 53:6): Rashi says that if a man was Mekadesh within three months and fled, the lenient opinion does not obligate a Get. Fleeing shows that he does not want to make Nisu'in within the forbidden time. This implies that if he did not flee, we excommunicate him until he divorces her; if he agrees to divorce her, we do not excommunicate him.

Question: We find that one must divorce only regarding a woman pregnant or nursing a baby from another man, but not within three months! Kidushin is no worse than Nisu'in, and after Nisu'in he need not divorce her, for this will not help, for already there is no Havchanah! Rather, we separate her until the end of three months, lest he profit from his sin. If so, separation should suffice also for one who was Mekadesh within three months! If not, people will mock Chachamim's words! The Niduy is for transgressing Chachamim's words. If he fled, this shows that he is submissive to and ashamed in front of Chachamim in his city, so this suffices, and we do not excommunicate him.

Rebuttal (Rosh): This does not refute Rashi. People will not mock Chachamim's words, for there is great reason to be more stringent about Kidushin than Nisu'in. After Nisu'in, divorce does not help! Why do we separate? Not every woman becomes pregnant immediately. There is concern for each Bi'ah, lest it make her pregnant. Therefore, whether he was Mekadesh or did Nisu'in, he divorces her until the end of three months. The Amora'im argued about Kidushin to teach that even though he did not do such a great Aveirah, we excommunicate him.

Nimukei Yosef (ibid.): Some derive from Rashi that if he did Nisu'in, we excommunicate him until he divorces her, or until the proper time for Nisu'in. The Ra'avad says so. Some say that even if he made Nisu'in, fleeing suffices.

Terumas ha'Deshen (216): A man married a nursing woman after 24 months including Adar Sheni. (We hold that Adar Sheni does not count.) They permitted him to stay, because Hagahos Maimoniyos mentions 24 months, but he did not say two years. B'Di'eved, one may rely on the lenient opinion.

Or Zaru'a (cited in Terumas ha'Deshen): We excommunicate until he divorces only if he was Mekadesh or made Nisu'in b'Mezid, but not if he was Shogeg, e.g. he did not know that she is nursing, or he is an ignoramus who did not know that a nursing woman is forbidden. He separates without a Get. It seems that a Get is only for Nisu'in, for separation suffices for Kidushin.

Terumas ha'Deshen: Only these cases are Shogeg, but if he knew of the Isur, he should have been concerned for Adar Sheni. This is not called Shogeg, and he must divorce her. In Yevamos we say that there is no enactment for a Kohen, for there is no Tana to rely on. This implies that if there were a Tana, we would rely on him, even if the Halachah does not follow him. Surely we did not seek leniencies for one who was Mezid. We should fine him harsher than letter of the law! If he was Shogeg, Or Zaru'a does not require a Get even for a Yisrael! Rather, he was Shogeg about a detail of the law, and we concluded that he must divorce her. Tosfos (Yevamos 36b DH v'Lo, citing the She'altos) holds that even for Kidushin, he must divorce her. We hold like them against Or Zaru'a. Perhaps likewise one may not rely on Or Zaru'a regarding Shogeg.

Shulchan Aruch (EH 13:10): If one was Mekadesh within 90 days, they would excommunicate him.

Beis Shmuel (15): If Niduy is so he will divorce her, it does not apply after three months. The Rambam does not require fleeing so far that he cannot return within three months, for he holds that fleeing atones for his sin, like exile. If so, he need not flee so far. The Mechaber brought only the Rambam's opinion (that we do not force him to divorce). Why did he bring (below) the Rosh's opinion that he must flee so far that he cannot return within three months? The Rambam taught about separation after Nisu'in (we do not say that it will not help). He did not need to teach about Niduy, for it follows (Kal va'Chomer) from Kidushin. The Magid Mishneh and Nimukei Yosef say so, unlike the Bach.

Rema: Some say that he must divorce her.

Gra (21): All the Meforshim except for the Rambam say so.

Rema: If he is a Yisrael, he may remarry her after 90 days. A Kohen may not remarry her. This is if he transgressed b'Mezid. If he was Mekadesh b'Shogeg, he need not divorce her, but we separate them. Some are stringent even about Shogeg.

Gra (22,23): This is a fine, and we do not fine Shogeg due to Mezid. The stringent opinion learns from the question about whether we enact for a Kohen. Surely we do not seek to be lenient for Mezid!

Rema (ibid.): For a Kohen, who may not remarry her, one may rely on the lenient opinion. For a Yisrael, one should not rely on the opinion that is lenient b'Shogeg.

Gra (24,25): This is like a Safek Yavam. There, we are lenient for a Kohen to rely on an opinion that we do not (normally) follow. Here, we rely on the Rambam.

Rema (ibid.): If Beis Din did not force him within 90 days, we do not force him after 90 days. They already transgressed. If he made Nisu'in, he must divorce her.

Beis Shmuel (17): The Darchei Moshe says that for a Kohen, even if he was Mekadesh b'Mezid, we may rely on the Rambam, and he need not divorce her.

Shulchan Aruch (ibid.): If he was Mekadesh and fled, we do not excommunicate him.

Chelkas Mechokek (8): Terumas ha'Deshen said that perhaps we are not lenient for Shogeg, and that a Chacham is not considered Shogeg. This is even for a Kohen, and even if another Chacham told him that it is permitted. We do not find that R. Yerucham disagrees about this. Terumas ha'Deshen was unsure about a Yisrael ignoramus, so we may rely on R. Yerucham who clearly permits, especially since the Rambam never obligates a Get. We may rely on the lenient opinion for a mid'Rabanan law.

Beis Shmuel (19): The Rambam holds that fleeing atones, so it helps even if he made Nisu'in. Some say that it shows that he will not made Nisu'in. If so, it does not help after Nisu'in. The Magid Mishneh and Nimukei Yosef hold that it helps even after Nisu'in.

Rema: We counsel him to flee.

Shulchan Aruch: Some say that he must flee so far that he cannot return within three months. It seems that the other Poskim disagree.

Yam Shel Shlomo (Yevamos 4:4): The Gemara discusses one who fled, not one who went away. This connotes that going to another city does not suffice. He must go where he is not known, and normally he would not go there. He flees from fear of Chachamim, who forbid him to be with his wife. Beis Din judges if it seems that he does not intend to made Nisu'in. No Mechaber gave the Shi'ur for fleeing; this is like I said.

Divrei Malkiel (4:123): We are stringent to require a Get even for Shogeg. However, if both traveled from their houses, this is like fleeing. We hold that fleeing suffices. Some say so even after Nisu'in. One may be lenient, for it is mid'Rabanan. The Tur is lenient even if he did not flee by himself, rather, he was commanded to flee. The Poskim do not require fleeing very far. If she went away, he may return to his house. Keneses ha'Gedolah says that it suffices for her to flee. This is wrong (if he made Nisu'in,), for some Poskim say that fleeing is to atone. Rashi says that it shows intent not to made Nisu'in, so it does not help after Nisu'in. Therefore, either way, it does not help. Keneses ha'Gedolah discussed before Nisu'in, according to Rashi. If he was commanded to flee, Rashi would hold that this does not help, for it does not reveal his intent. Darchei Moshe brings from R. Yerucham that a separation of two or three days journey suffices. We do not require as much as for fleeing. This connotes like the Rosh, that fleeing is so far that he cannot return within the time. The Shulchan Aruch said that one need not flee so much. He did not say how far one must flee. It seems that R. Yerucham requires at least two days journey. Tosfos (Mo'ed Katan 21b DH Makom) brings from Bahag that within one day is called close. More than this is far; it need not be two full days. Yam Shel Shlomo says that going to another city does not suffice. I say that if fleeing is to atone, another city suffices. For a murderer, exile to another neighborhood suffices! Even from the Beis ha'Keneses to the street is called exile! (Ta'anis 16a) However, here going to another neighborhood does not suffice, for that is separation.

Maharitatz (Chadashos 43): The Rambam would not require fleeing far, but if he was commanded to flee, perhaps it must be far away, and it must be painful and shameful.