Rather, Rava said that the light prohibition is actually that of a married woman. And similarly, when Ravin came from Eretz Yisrael, he said that Rabbi Yoḥanan said that the baraita is referring to a married woman. And for what reason does the tanna call this a light prohibition? The reason is that it differs from and is more lenient than other prohibitions in that her husband, who renders her forbidden, does not render her forbidden for his whole lifetime, as he can negate the prohibition by giving her a bill of divorce. This is also taught in a baraita: Abba Ḥanan said in the name of Rabbi Elazar: The baraita is referring to a married woman.

The Gemara explains that according to this opinion the a fortiori inference should be understood as follows: And if in a case where he has relations with a married woman, which is a light prohibition, due to the fact that he who renders her forbidden does not render her forbidden for his whole lifetime, and yet the one who renders her forbidden is forbidden, as the husband of a woman who committed adultery is permanently barred from having relations with her, then the following conclusion is correct: One who has relations subject to a severe transgression, e.g., a wife’s sister, which is severe because the one who renders his wife forbidden renders her forbidden for her whole lifetime, since as long as his wife remains alive he is forbidden to her sister, is it not right that the one who renders her forbidden should be forbidden?

The verse therefore states: “Her,” from which it is derived: It is her intercourse that renders her forbidden, but the intercourse of her sister does not render her forbidden.

§ The mishna taught: Rabbi Yosei says: Whoever disqualifies others also disqualifies himself, and whoever does not disqualify others does not disqualify himself. The Gemara asks: What is it Rabbi Yosei is saying? If we say that the first tanna said that one’s wife and brother-in-law went overseas and he mistakenly had relations with his wife’s sister, who is married to his brother-in-law, and consequently the wife of his brother-in-law is forbidden to the brother-in-law, and his wife is permitted to him, this is problematic.

The Gemara elaborates: And according to this explanation, Rabbi Yosei says to the first tanna: Just as his wife is permitted to him, the wife of his brother-in-law is also permitted to her husband. Rabbi Yosei’s reasoning is that if he has not disqualified his wife to himself, due to the accidental nature of his relations with her sister, he should not disqualify the sister to her husband either. The Gemara continues: If so, the formulation of Rabbi Yosei’s statement is imprecise, as instead of saying: Whoever does not disqualify others does not disqualify himself, he should have said: Whoever does not disqualify himself, i.e., his sexual relations do not render his wife forbidden to him, does not disqualify others, i.e., the wife of the other man.

But rather, one might explain Rabbi Yosei’s teaching in the reverse manner: Just as the wife of his brother-in-law is forbidden to her husband, his own wife is also forbidden to him. This works out well with regard to the clause that starts with: Whoever disqualifies, as he disqualifies others, i.e., his brother-in-law’s wife to his brother-in-law, and therefore he also disqualifies his wife to himself. However, the continuation of the statement: Whoever does not disqualify, what is its purpose? This clause has no apparent relevance to Rabbi Yosei’s statement.

Rabbi Ami said: Rabbi Yosei’s statement does not refer to this halakha, but to the first mishna of the chapter, which taught that if a woman whose husband went overseas was informed that he was dead and she married by permission of the court she must leave her new husband and is exempt from bringing an offering. If she married based on the testimony of witnesses, without the authorization of the court, she must leave and is liable to bring an offering. In this regard, the power of the court is enhanced, as she is exempt from an offering.

Rabbi Ami explains: And accordingly, if his wife and brother-in-law went overseas and witnesses came and testified that they were both dead, the first tanna says that it is no different whether the wife of his brother-in-law married him based on the testimony of witnesses alone, in which case the wife of his brother-in-law is permitted to her husband, as she is considered as having acted under duress, having heard testimony that her husband was dead, and it is no different if she married him by permission of the court, as although the wife of his brother-in-law is prohibited, his own wife remains permitted to him.

Rabbi Ami continues his explanation. And Rabbi Yosei says to the first tanna: One who married by permission of the court, who disqualifies others, he also disqualified himself to his own wife; however, in the case of one who married based on the testimony of witnesses who does not disqualify others, I agree that he does not disqualify himself, and his wife is permitted to him.

Rabbi Yitzḥak Nappaḥa said: Actually, Rabbi Yosei is referring to the latter clause of the mishna, and the explanation is as follows: This is referring to one who married his brother-in-law’s wife, and that case is referring to one who married his brother-in-law’s betrothed. Alternatively, this involves a situation where his betrothed and his brother-in-law went overseas, whereas that concerns a situation when his wife and his brother-in-law went abroad. And the first tanna said: It is no different whether the ones who left were his wife and his brother-in-law, and it is no different whether they were his betrothed and his brother-in-law. Either way his brother-in-law’s wife is forbidden to her husband and his own wife or betrothed is permitted to him.

Rabbi Yitzḥak Nappaḥa continues his interpretation. And Rabbi Yosei said to the first tanna: If his wife and his brother-in-law left, in which case it cannot be said that he had a condition with regard to his marriage to his wife, i.e., that the finalization of the marriage was pending on the fulfillment of some condition, everyone would realize that his marriage to her sister was a mistake and she is therefore permitted to his brother-in-law. Consequently, as he does not disqualify another, he does not disqualify himself either. If, however, it was his betrothed and his brother-in-law who left, when it can be mistakenly said that he had a condition with regard to his betrothal and the condition was unfulfilled, his brother-in-law’s wife is therefore prohibited from returning to his brother-in-law. And therefore, as he disqualifies others he also disqualifies himself, and his betrothed is forbidden to him.

§ Rav Yehuda said that Shmuel said: The halakha is in accordance with the opinion of Rabbi Yosei. Rav Yosef strongly objects to this: And did Shmuel actually say this? But wasn’t it stated that they disputed the status of a yevama: Rav said that she is like a married woman, and Shmuel said that she is not like a married woman. And Rav Huna said that this dispute concerns a case where his brother betrothed a woman and that brother went off overseas, and the one left behind heard that his brother was dead and he arose and married his brother’s wife, in levirate marriage, and subsequently the missing brother returned.

As Rav said that she is like a married woman who married another man based on testimony that her husband was dead and is therefore forbidden to the yavam, i.e., to her first husband, who is called the yavam after his brother married her. And Shmuel said that she is not like a married woman, and is permitted to him. This apparently contradicts Rav Yehuda’s ruling in the name of Shmuel that the halakha is in accordance with the opinion of Rabbi Yosei, as here too people might mistakenly think that the original betrothal included an unfulfilled condition and she should therefore be forbidden to him as the wife of his brother.

Abaye said to Rav Yosef: And from where do you know that when Shmuel said that the halakha is in accordance with the opinion of Rabbi Yosei, he was speaking of the explanation of Rabbi Yitzḥak Nappaḥa with regard to Rabbi Yosei’s opinion? Perhaps he was speaking of the explanation of Rabbi Ami, that Rabbi Yosei is referring to the difference between one who married by permission of the court and one who did so based on the testimony of witnesses. And even if one accepts the claim that Shmuel’s ruling endorses the interpretation of Rabbi Yitzḥak Nappaḥa, from where do you know that he was referring to the clause: One who disqualifies?