Yevamos 4:13-5:1

Yevamos 4:13

According to Rabbi Akiva, a mamzer is the offspring of any sexual union prohibited by the Torah; Shimon HaTimni, however, limits it to relationships for which one would be punished by kareis. The halacha follows this latter opinion. Rabbi Yehoshua says a mamzer is the product of any relationship that is a capital offense. Rabbi Shimon ben Azzai found a scroll in Jerusalem listing family histories. This scroll reported that a certain person was a mamzer because his mother was a(n adulterous) married woman, which confirms Rabbi Yehoshua’s position. If a man’s wife dies, he may marry her sister. If he divorces his wife and she subsequently dies, he may marry her sister. If she married another man and then died, he may marry her sister. If his deceased brother’s widow, who is waiting to perform yibum, dies, he may marry her sister. If he performed chalitzah with the widow and she subsequently died, he may marry her sister.

Yevamos 5:1

(“Maamar” is when a man marries his brother’s widow with a contract or money but he has not actually performed yibum yet.) Rabban Gamliel says that there is no divorce after divorce, there is no maamar after maamar, there is no yibum after yibum and no chalitzah after chalitzah [i.e., if there are two widows and a brother performs any of these acts with one of them, the concept is completely inapplicable with the other woman]. The Sages say that there is divorce after divorce and maamar after maamar but they agree that there is nothing after yibum or chalitzah.