The Gemara asks: Isn’t it obvious that his claim is deemed credible with regard to someone inheriting from him? Since he could have given this person his property as a gift, it need not be stated that his claim is accepted with regard to his inheritance. The Gemara responds: It was necessary for the mishna to state that his claim is deemed credible with regard to rendering his wife exempt from levirate marriage despite the fact that it is not in his power to render her exempt, but the halakha of inheritance is not a novelty.

The Gemara asks: We already learned this in a mishna (Kiddushin 64a) as well: One who said at the time of his death: I have children, is deemed credible, and his wife is thereby exempt from levirate marriage. If he said: I have brothers, and his wife therefore must enter levirate marriage, he is not deemed credible.

The Gemara answers: There, in that mishna, it is a case where he is not presumed by us to have a brother. Therefore, his wife is already presumed to be exempt from levirate marriage, and his claim that he has a son merely substantiates this presumption. Here, the mishna adds a novelty that even if he is presumed to have a brother, his claim that he has a son is accepted, and his wife is thereby exempted from levirate marriage.

Rav Yosef says that Rav Yehuda says that Shmuel says: For what reason did the Sages say that one who says: This is my son, is deemed credible? Since a husband who says: I divorced my wife, is deemed credible, and his wife is thereby exempt from levirate marriage, he is deemed credible with regard to this claim as well.

As Rav Yosef forgot some of his Torah knowledge due to an illness, he questioned the accuracy of his citation of Rav Yehuda. Rav Yosef said: Master of Abraham! This reasoning makes that which is taught in the Mishna dependent upon that which is not taught, as the credibility of one who claims: This is my son, is stated in the mishna, while the halakha that a husband’s claim that he divorced his wife is accepted is the statement of an amora.

Rather, if this explanation was stated, it was stated like this: Rav Yehuda says that Shmuel says: For what reason did the Sages say that one who says: This is my son, is deemed credible with regard to rendering his wife exempt from levirate marriage? Since it is in his power to divorce her and thereby render her exempt from levirate marriage, he is deemed credible with regard to this claim as well.

Rav Yosef said in addition: Now that you said that we say that the husband is deemed credible since he has the power to divorce her, a husband who says: I divorced my wife, is also deemed credible, since it is in his power to divorce her at any time.

When Rav Yitzḥak bar Yosef came from Eretz Yisrael to Babylonia, he said that Rabbi Yoḥanan says: A husband who says: I have divorced my wife, is not deemed credible. Rav Sheshet waved his hand disparagingly, as if to say that Rav Yosef’s statement that he is deemed credible since it is in his power to divorce her is gone due to Rabbi Yoḥanan’s statement.

The Gemara asks: Is that so? Did Rabbi Yoḥanan actually say that? But doesn’t Rabbi Ḥiyya bar Avin say that Rabbi Yoḥanan says: A husband who says: I have divorced my wife, is deemed credible?

The Gemara answers: That is not difficult. Here, in the statement that the husband is not deemed credible, Rabbi Yoḥanan was referring to a retroactive testimony. For example, in a case where he testified that he divorced her on a certain date, and it is discovered that she engaged in sexual intercourse with another man after that date, his testimony is not accepted concerning whether the woman is liable to receive punishment; she is not considered to have been divorced at the time. This is because it is not in the husband’s power to divorce her retroactively.

By contrast, the statement there, where Rabbi Yoḥanan said that the husband’s testimony is deemed credible, refers to testimony for the future, e.g., where he says that he divorced her on that same day, or without specifying a date, in which case his statement is relevant only for the future. Since it was in his power to divorce her at that time, his testimony is deemed credible; if he dies, she is exempt from levirate marriage, and if she engages in sexual intercourse with another man, she is not considered to have committed adultery.

A dilemma was raised before the Sages: If the husband said that he divorced his wife on a certain date, as a retroactive testimony, what is the halakha concerning his testimony being deemed credible and accepted with regard to the future, rendering her divorced from that time onward, despite the fact that his claim is not accepted with regard to the past?

The dilemma is based on the following fundamental question: Do we divide the husband’s statement, accepting that he divorced his wife inasmuch as she is considered divorced from that time onward, since it is in his power to divorce her now, even though his claim that he divorced her in the past is not accepted? Or do we not divide the statement, and say instead that his claim is rejected altogether, since his claim concerning the past cannot be accepted? Rav Mari and Rav Zevid engaged in a dispute with regard to this issue. One says that we divide the husband’s statement, and one says that we do not divide it.

The Gemara asks: In what way is this case different from Rava’s statement? As Rava says that if a man says: So-and-so engaged in sexual intercourse with my wife, the husband and another witness combine to kill him, i.e., to have him sentenced to death for adultery. The Gemara infers: He combines with another witness to kill him, but not to kill her. The wife is not sentenced to death based on this testimony, even if they testified that she engaged in sexual intercourse willingly, as a husband is disqualified from bearing witness concerning his wife. Evidently, the husband’s testimony is divided; his testimony concerning the man is accepted even though the testimony concerning his wife’s part in the same action is rejected.

The Gemara answers: With regard to two separate bodies we divide the statement. Therefore the husband’s testimony is accepted with regard to the man but rejected with regard to his wife. With regard to one body we do not divide it. That is why one Sage holds that a husband’s claim that he divorced his wife in the past cannot be divided, so that his claim that he divorced her would be accepted while his claim as to when he divorced her would be rejected.