Gemara

(Mishnah): If a girl became Mekudeshes, divorced, Mekudeshes, then widowed (before Bagrus), her father gets the Kesuvah.

Inference: The Tana discusses when she was divorced and widowed, but not when she was widowed twice (for this is severe), for then she could not remarry!

Our Stam Mishnah is like Rebbi, who says that after she is widowed twice, the Chazakah is that her husbands will die.

Yevamos 26a (Mishnah): Whenever Reuven may not marry Leah because he permitted her to marry (he brought her Get or testified that her husband died), if Leah married someone else and was widowed or divorced, Reuven may then marry her.

Suggestion: This is even if Leah was widowed now and (remarried and) widowed again, or was divorced now and divorced again. This is unlike Rebbi, who says that a Chazakah is established after two occurrences!

Rejection: It can be like Rebbi. The Mishnah permits a widowed woman who was later divorced, and a divorced woman who was later widowed.

64b (Beraisa - Rebbi): If a woman circumcised two of her sons and they died, she should not circumcise her third son;

R. Shimon ben Gamliel says, she circumcises the third, but not a fourth.

Question: Whom does the Halachah follow?

Answer (Rav Yitzchak bar Yosef): A case occurred in which Leah's first two sons died in circumcision. R. Yochanan told her to circumcise her third son.

Abaye protested that Rav Yitzchak permits an Isur and a danger. Nevertheless, Abaye relied on him and married Chomah, who had been widowed twice. Abaye died in her lifetime.

Objection #1 (Rava): Why did Abaye jeopardize his life?! He himself said that we may rely on Avin, who reviews his learning, but not on Yitzchak, who does not!

Objection #2: They argue about circumcision. Do they argue about marriage?

Answer (to Objection #2 - Beraisa - Rebbi): If a woman was widowed twice; she may not marry again;

R. Shimon ben Gamliel says, she may marry a third man, but not a fourth.

Rishonim

Rambam (Hilchos Isurei Bi'ah 21:31): If a woman was widowed from two men she may not marry again. If she married a third man she may remain with him. If he was only Mekadesh her, he may make Nisu'in.

Magid Mishneh: We do not add to the decrees of Chachamim. The Gemara lists cases when we force men to divorce; it did not mention Katlanis. Kidushin is like Nisu'in (for this law), therefore he may keep her.

Kesef Mishneh: The Rivash says that even if Beis Din warned her third husband beforehand, he need not divorce her. In a Teshuvah, the Rambam says that Katlanis is not a real danger or Isur. It is a mere Nichush (superstition), fear and panic prone to strike physically weak people.

Rosh (Kesuvos 4:3, citing R. Moshe bar Yehudah): The Mishnah did not discuss when she was widowed twice, for then she would not have a Kesuvah from the second husband, for retroactively we find that she is a Katlanis. The Kesuvah is paid 'when you will (be permitted to) marry another man'. Since she may not remarry, she gets no Kesuvah.

Rebuttal (Rosh): A barren woman may marry a third man only if he has children (Yevamos 65a). If she married a childless man, he divorces her without a Kesuvah. This implies that she receives a Kesuvah from her second husband. The Gemara asks whether or not her first two husbands may demand back the Kesuvah if she is childless also from the third man. This shows that they paid Kesuvos, even though the Tana is Rebbi, who establishes her to be barren after two marriages. This is because for monetary matters we do not rely on Chazakah until three occurrences, like Shor ha'Mu'ad. Also regarding Katlanis, we apply 'when you will (be permitted to) remarry' because one can Mekadesh her, and if she married we do not force her husband to divorce her. Therefore she has a Kesuvah from her second husband, and from the third only if he knew that she was widowed twice. We force her third husband to divorce her, because we are more stringent about danger than about Isurim.

Question (Tif'eres Shmuel 1): Just above, the Rosh said that we do not force him to divorce her! We must say that he said so according to his Rebbeyim.

Ran (Kesuvos 15a DH Gemara): The Gemara says that had she been widowed twice, she could not remarry. It did not say that she would not get a Kesuvah. Some infer from this that she gets a Kesuvah even from the third husband. This is because it is not her fault; Shomayim decreed that her husbands die. If she would not receive a Kesuvah from the third, she would not get even from the second, for our Tana holds that two deaths establish the Chazakah, and we find that it was a Mekach Ta'os.

Rebuttal (Ran): Surely she does not get a Kesuvah from the third husband if she did not inform him. She deceived him! However, she gets from the second husband. Even though she is established to be a Katlanis, it is not clear that her husbands died due to her. Perhaps it was their time to die! Rav Acha Gaon says that 'when you will (be permitted to) remarry' excludes only when she cannot remarry due to the husband she left (e.g. she fell to Yibum). Rava apportioned food (which is done only for one who receives a Kesuvah) to Chomah after Abaye died, even though she was widowed twice before, because Abaye knew this. However, she may not remarry because there are grounds to say that her husbands died due to her.

Beis Shmuel (EH 9:4): Tosfos (Yevamos 65a DH Nises) asks why (regarding a barren woman) we follow the majority (of women who can conceive) regarding money (she gets a Kesuvah from her second husband), but not regarding Isur (she may not marry a third). Normally, we follow the majority for Isur but not for money! The Ran (above) answers this.

Nimukei Yosef (Kesuvos 15a DH b'Nisu'in, citing the Ritva): If one wants to marry a Katlanis, we do not allow him to harm himself. It is forbidden, in the category of suicide. We excommunicate him in Beis Din until he divorces her. Our Rebbi did so in practice.

Poskim

Shulchan Aruch (EH 9:1): If a woman was married (Rema - or Mekudeshes) to two men and they died, she may not marry a third man. If she did, she may remain with him.

Note: Even though the Mechaber says 'Niseis', which connotes Nisu'in, surely he does not exclude Kidushin. (See Beis Yosef DH v'Da.) The Rema explains that the Mechaber includes Kidushin.

Beis Yosef (DH veha'Rashba): The Rashba did not know the Rambam's source for this. Perhaps it is because the Gemara did not say that he must divorce her. Alternatively, Abaye did not divorce Chomah, even though he heard that his Rebbeyim Rabah and Rav Yosef ruled like Rebbi regarding Nisu'in. Also Rava, who was shocked that Abaye married her, did not force him to divorce her. Alternatively, the Gemara (Yevamos 26a) suggested that the Mishnah discusses a woman widowed twice and a woman divorced twice. Some say that a woman divorced twice may not remarry, but surely if she did she need not be divorced. The same applies to a woman widowed twice.

Gra (2): The Rambam learns from Yehudah, who kept Tamar - "V'Lo Yosaf Od Ledatah" (Sotah 10b). Alternatively, he learns from Abaye. The Rosh disagrees, for whenever there is danger we force a husband to divorce, e.g. a Mukas Shechin or one who married a woman pregnant with or nursing another man's baby.

Shulchan Aruch (ibid.): She has a Kesuvah from her third husband only if he knew that she was widowed twice. She has a Kesuvah from her second husband even if he did not know that she was widowed before.

Beis Yosef (DH u'Mah she'Chosav Rabeinu v'Im): R. Yerucham brings an opinion that she has no Kesuvah even from her second husband. The Rosh rejected this opinion.

Chelkas Mechokek (1): We do not discuss one who wants to keep his wife after learning that she is a Katlanis. Surely, he may not keep her without a Kesuvah! Rather, he found out and wants to divorce her, or it became known after he died. The Rambam says 'Lo Tetzei', which connotes that this is like every case when the Gemara says Lo Tetzei, i.e. he may not divorce her without a Kesuvah. This is because he holds that it is not a Ta'os; it is a mere fear that affects weak people. He cannot divorce her against her will due to R. Gershom's Cherem.

Rebuttal (Beis Shmuel 3): R. Gershom did not decree about Safek mortal danger.

Question (Chelkas Mechokek): The Shulchan Aruch blended the Rambam's opinion (she may remain with a third husband) with that of the Rosh, who holds that it is a Mekach Ta'os (so she has no Kesuvah unless he knew)!

Answer (Beis Shmuel 3): Perhaps the text of the Shulchan Aruch should say 'some say that she must leave, and if he knew, she has a Kesuvah.' This explains why the Rema did not bring the majority opinion, i.e. of the Rosh. Alternatively, he need not pay a Kesuvah because he can say 'I hold like the Rosh', and he need not divorce because he can say 'I hold like the Rambam'.

Rema: Some say that this is only if they died normally, but if one husband was killed, died through petilence, fell from the roof or similar matters, we are not concerned. Therefore, many are lenient about these and we do not protest.