Talmud - Yevamot 98b יבמות צ״ח ב׳

If she is his father’s paternal half sister, he may maintain her as his wife. If she is his mother’s maternal half sister, he must divorce her. If she is his mother’s paternal half sister, Rabbi Meir says he must divorce her, and the Rabbis say he may maintain her. This is as Rabbi Meir would say: Any relative forbidden due to kinship with the mother, whether the woman is his paternal relative, e.g., his father’s maternal half sister, or his maternal relative, he must divorce her. However, if she is forbidden due to the father, he may maintain her.

And he is permitted to marry his maternal brother’s wife and his father’s brother’s wife, and all other forbidden relatives are also permitted to him. The expression: And all other relatives are also permitted to him, is added to include the father’s wife.

With regard to one who married a woman and her daughter and they converted, he may remarry one but must divorce the other one. He should not marry her ab initio. If his wife, the daughter, died, he is permitted to maintain his mother-in-law as his wife. And some teach that he is prohibited from maintaining his mother-in-law.

In any event, this baraita teaches that he is permitted to marry his brother’s wife. The Gemara asks: What, is it not referring to a case where his brother married her when he was already a convert? The Gemara answers: No, it is referring to a case where he married her while he was a gentile. The Gemara asks: If so, what is the purpose of stating this obvious halakha? The Gemara answers: Lest you say that the Sages should decree that the marriage is prohibited if the brother married her while he was a gentile, due to the prohibition against their marriage if the brother married her when he was already a convert. The baraita therefore teaches us that there is no such decree.

The Master said: If one married a woman and her daughter and they converted, he may remarry one but must divorce the other one. He should not marry her ab initio. The Gemara asks: Now that he must divorce her, is it necessary to state that he should not marry her ab initio? The Gemara answers: That statement is standing there, i.e., it is referring to the previous sentence, and this is what it is saying: Those wives that the Sages said that he may maintain, e.g., his paternal half sister, he should not marry them ab initio.

The baraita taught: If his wife, the daughter, died, he is permitted to maintain his mother-in-law as his wife. And some teach that he is prohibited to maintain his mother-in-law. The Gemara comments: One of the teachings is in accordance with the opinion of Rabbi Yishmael, and the other one is in accordance with the opinion of Rabbi Akiva.

The one who prohibits the convert from maintaining his mother-in-law is in accordance with the opinion of Rabbi Yishmael, who said that one’s mother-in-law after his wife’s death remains forbidden to him to the same degree as during her lifetime. And therefore, with regard to a convert, the Sages decreed that she is forbidden to him, lest one marry his mother-in-law who is a Jew from birth after his wife’s death. And the one who permits him to maintain her is in accordance with the opinion of Rabbi Akiva, who said that the prohibition against engaging in intercourse with one’s mother-in-law is weakened after his wife’s death, as they are not liable to receive the death penalty. And therefore, with regard to a convert, the Sages did not decree that she is forbidden to him.

MISHNA: With regard to five women whose offspring were mixed, i.e., their lineage became indeterminate, and they had other sons as well who were not mixed, and the mixed sons matured and married women and subsequently died, then four sons who were not mixed, each one from a different mother, must perform ḥalitza with one of the widows, as she might be the sister-in-law of any of them. And one son of the mother whose sons did not perform ḥalitza may perform levirate marriage with her instead of ḥalitza; even if she is not his sister-in-law, once she has received ḥalitza from the others she may marry any man.

Subsequently, he and three of the four other sons must perform ḥalitza with one of the remaining widows, and the other one may perform levirate marriage. When this process has been completed for all the widows, four ḥalitzot and a levirate marriage are found altogether for each and every widow.

GEMARA: The Gemara infers from the mishna that ḥalitza specifically is performed first, and afterward levirate marriage. However, levirate marriage may not be performed first, as that would breach the prohibition against a yevama engaging in intercourse with a member of the public, if she is not his sister-in-law.

The Gemara asks: What is the reason for the mishna’s ruling that the son who performed levirate marriage and three of the four others must perform ḥalitza with one of the remaining widows, and the remaining son may perform levirate marriage? Why can’t the same son who performed levirate marriage with the first widow be the one to perform levirate marriage with the other widows, too, after the other four sons perform ḥalitza? The Gemara answers: Do not say that one of the brothers may perform levirate marriage with all of them. Rather, each one of them should perform levirate marriage with one, as perhaps one will happen upon his own sister-in-law, whereas if one performs levirate marriage with all of them, the others will not have a chance to perform the mitzva.

§ A continuation of a case in the mishna is stated in a baraita: If some of them are brothers, and some of them are not brothers, the brothers perform ḥalitza and those who are not brothers perform levirate marriage. The Gemara asks: What is the baraita saying? Rav Safra said that this is what it is saying: If some of the sons who were not mixed are only paternal brothers of the mixed sons, and some of them, in addition to being paternal half brothers, are also maternal half brothers of other members of the mixed group, then the maternal half brothers must perform ḥalitza with all of the women, since each of them might be his maternal sister-in-law, who is forbidden to him, as levirate marriage applies only to a paternal sister-in-law. And those who are only paternal brothers perform levirate marriage.

The baraita continues: If some of them are priests and some of them are not priests, the priests perform ḥalitza, and those who are not priests perform levirate marriage, as it is prohibited for a priest to marry a woman who underwent ḥalitza. If some of them are priests and some of them are maternal half brothers, both these and those perform ḥalitza and not levirate marriage.

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

Yevamot 98b examines forbidden marriage ties among converts, focusing on rules for half-sisters, in-laws, and a wife-and-daughter conversion case.