to permit a rival wife in a place where the mitzva of levirate marriage is not applicable. What is the reason, i.e., how is this inferred? The verse states: ''With her.'' In other words, it is in a place where the obligation ''her brother-in-law will have intercourse with her'' is applicable that a rival wife is prohibited, whereas in a place where the obligation ''Her brother-in-law will have intercourse with her'' is not applicable, a rival wife is permitted.

Rami bar Ḥama said to Rava: If the phrase ''with her'' is referring only to a case where levirate marriage is applicable, one can say that a forbidden relative herself should be permitted in a place where the mitzva of levirate marriage is not applicable. According to this interpretation, the prohibitions with regard to all those with whom relations are forbidden are in effect only when levirate marriage applies. Rava answered: And is it not an a fortiori inference? If these relatives are prohibited in a place where there is a mitzva, could they be permitted in a place where there is no mitzva?

Rami bar Ḥama said to Rava: That is no proof, as the case of a rival wife herself can prove that this a fortiori inference is incorrect, as in a place where there is a mitzva she is prohibited and in a place where there is no mitzva she is permitted. Rava said to Rami bar Ḥami: With regard to your claim, the verse states: ''And you shall not take a woman to her sister…in her lifetime'' (Leviticus 18:18). This indicates that all cases in which it is in the lifetime of her sister she is forbidden, even when no mitzva applies.

The Gemara asks: This phrase ''in her lifetime'' is necessary, as indicated by the plain meaning of the phrase, to exclude the time after death, i.e., to teach that a wife’s sister is forbidden only while the wife is still alive, whereas after her death the sister is permitted. The Gemara answers: That halakha that a woman is permitted after her sister’s death is derived from ''and you shall not take a woman to her sister'' (Leviticus 18:18), as when one of them is dead it is no longer considered ''a woman to her sister.''

The Gemara further asks: If this halakha is derived from ''a woman to her sister,'' I would say that even if she were divorced, her sister is permitted. Therefore, the verse states: ''In her lifetime,'' which indicates that the prohibition is in effect in all cases that are in her lifetime. This teaches that although she is divorced, her sister is not permitted.

§ Rather, the Gemara suggests a different interpretation. Rav Huna bar Taḥlifa said in the name of Rava: Two verses are written, i.e., two separate issues are mentioned in the same verse. It is written: ''And you shall not take a woman to her sister, to be a rival [litzror],'' which indicates that two rival wives are prohibited. And it is written: ''To uncover her nakedness'' (Leviticus 18:18), in the singular, which means one and not both of them. How is it possible to reconcile this apparent contradiction? In a place where there is a mitzva of levirate marriage, both the forbidden relation and her rival wife are prohibited. In a place where there is no mitzva of levirate marriage, the forbidden relation is prohibited but her rival wife is permitted.

The Gemara raises a difficulty: I can reverse this and suggest the opposite. In a place where there is a mitzva, the forbidden relation is prohibited and her rival wife is permitted, and in a place where there is no mitzva, both of them are prohibited. The Gemara answers: If so, let the verse not say ''with her,'' at all, as this superfluous phrase teaches that the prohibition with regard to a rival wife applies only when there is a mitzva of ''her brother-in-law will have intercourse with her.''

Rav Ashi said to Rav Kahana: From where is it derived that this superfluous phrase ''with her,'' comes to prohibit, i.e., although there is an obligation that ''her brother-in-law will have intercourse with her,'' a wife’s sister remains prohibited? Perhaps it serves to permit, and this is what the Merciful One is saying: ''You shall not take a woman to her sister, to be a rival'' (Leviticus 18:18), i.e., neither her nor her rival wife. When is this the case? It is in a place where the obligation of ''her brother-in-law will have intercourse with her'' does not apply. However, in a place where ''with her'' does apply and there is an obligation of levirate marriage, both of them are permitted.

Rav Kahana replied to Rav Ashi: If the above statement is so, and ''to uncover her nakedness'' is referring to one woman, under what circumstances can you find this case? When is only one of them prohibited? If it is in a place where there is a mitzva, they are both permitted; if it is in a place where there is no mitzva, they are both forbidden. Therefore, the earlier line of reasoning must be accepted: A rival wife is forbidden only in a case where the mitzva of levirate marriage is in effect.

§ While clarifying the exposition of the phrase ''with her,'' an alternative interpretation attributed to Rabbi Yehuda HaNasi was mentioned. The Gemara discusses the matter itself. Rabbi Yehuda HaNasi says: The verse does not say have intercourse, but ''have intercourse with her.'' And it does not say and consummate the levirate marriage, but ''and consummate the levirate marriage with her.'' These phrases serve to prohibit rival wives and women with whom relations are forbidden. The Gemara asks: Are rival wives written here? In other words, what is the connection between the verse and the topic of rival wives, an issue that is not even mentioned in the verse? And furthermore: The prohibition with regard to rival wives is derived from the phrase ''To be a rival wife [litzror],'' not from this source.

The Gemara answers: Rabbi Yehuda HaNasi derives a different halakha from the phrase ''to be a rival wife,'' in accordance with that statement of Rabbi Shimon. In Rabbi Shimon’s opinion, the exemption of two sisters from levirate marriage applies not only when the yavam is married to one of the sisters, but also if two sisters who come before him for levirate marriage were previously married to two of his brothers. In that case, the levirate bond itself is sufficient for them to be considered rival wives of one another.

And with regard to the previous question: Are rival wives written here? The answer is that this is what he is saying: If so, that the verse does not come to exempt rival wives, let the verse state only: Have intercourse. What is the meaning of ''have intercourse with her''? It serves to limit the case to one woman and not two, in the following manner: Anywhere that there are two possibilities of having intercourse, i.e., there is a choice between marrying one of two women in levirate marriage, in such a way that if he wants he may marry this one, and if he wants he may marry that one, then each one is permitted. And if he does not have a choice and is obligated to marry one of them, e.g., if the other is a forbidden relation to him, they are both prohibited, including the rival wife.

When the verse states: ''And consummate the levirate marriage with her,'' it comes to teach the following. It is in a place where levirate marriage is applicable that a rival wife is prohibited, whereas in a place where levirate marriage is not applicable, a rival wife is permitted. The Gemara asks: And with regard to the Rabbis, who do not interpret the verse in this manner, what do they do with this emphasis on ''have intercourse with her''? How do they interpret it?

The Gemara responds: They need this for that which Rabbi Yosei bar Ḥanina said, as Rabbi Yosei bar Ḥanina said: ''And have intercourse with her'' means marriage, i.e., she is fully his wife from that moment onward. This teaches that he divorces her with a bill of divorce after levirate marriage, and she can no longer be released by ḥalitza, and he may subsequently remarry her if he so wishes. And the verse ''and consummate the levirate marriage with her,'' this means against her will. Although betrothal in general does not take effect without the woman’s consent, levirate marriage can be effected against her will.

The Gemara asks: And from where does Rabbi Yehuda HaNasi derive these widely accepted halakhot? The Gemara responds: That halakha cited by Rabbi Yosei bar Ḥanina, that a woman taken in levirate marriage has the status of a regular wife who may be divorced and remarried, is derived from the verse ''and take her to him to be his wife'' (Deuteronomy 25:5), which means that she will be his wife for all purposes, like any other wife. And the halakha that levirate marriage can be effected against her will is derived from ''her brother-in-law will have intercourse with her,'' which indicates that it can be achieved without her consent.

The Gemara asks: And what does Rabbi Yehuda HaNasi do with this superfluous phrase, ''with her''? The Gemara responds: He needs it for that which is taught in a baraita with regard to a different matter. The Sages said: The court is obligated to bring a bull as a sin-offering for an unwittingly committed communal sin on account of an erroneous halakha they taught only for a matter whose intentional transgression incurs karet and whose unwitting violation necessitates the sacrifice of a sin-offering. And similarly, the anointed High Priest, who also brings a bull for an unwittingly committed sin, is obligated to do so only if his mistake involved a matter whose intentional transgression incurs karet and whose unwitting transgression necessitates the sacrifice of a sin-offering.