- The rules of lineage where kiddushin is permitted or forbidden
The Mishnah on the previous Daf taught: כל מקום שיש קידושין ואין עבירה – Anywhere there is effective kiddushin and there is no transgression in the marriage, הולד הולך אחר הזכר – the offspring follows the lineage of the male (e.g., Kohen, Levi, and Yisroel). Where the marriage is prohibited, הולד הולך אחר הפגום – the offspring follows the blemished parent (such as a mamzer). This first rule is challenged from a Baraisa, in which Rebbe Yose said: גר שנשא ממזרת הולד ממזר – a convert who married a mamzeres, which he holds is permitted, the offspring is a mamzer. The Gemara answers that the Mishnah does not follow Rebbe Yose’s opinion, but that of Rebbe Yehudah, who holds a convert may not marry a mamzeres. The Mishnah does not write it explicitly, because it is included by the general term "כל מקום". Alternatively, the Tanna can be Rebbe Yose, because the Mishnah implies there are exceptions to its rule.
The Gemara discusses other cases not listed by the Mishnah and explains how they are either included or excluded by the Mishnah’s terms.
- באומות הלך אחר הזכר נתגיירו הלך אחר הפגום שבשניהם
Ravin quoted Rebbe Yochanan: באומות הלך אחר הזכר – With gentile nations, follow the male regarding the offspring. נתגיירו הלך אחר הפגום שבשניהם – If they converted, follow the blemished one from the two of them. The first statement is explained with a Baraisa teaching that if a member of the nations other than the seven nations of Canaan has a child from a Canaanite woman, the child can be acquired as a slave, like his father (and is not condemned to death, as his mother is). However, if a Canaanite slave fathers a child from a non-Canaanite woman, the child is considered a Canaanite and must be killed, like his father. The second statement is explained: בעמוני שנשא מצרית – a male Ammonite convert who married a female Egyptian convert: if their child is male, שדיא אבתריה דידיה – cast him after [his father], because for a male, the Ammonite parent is a greater blemish (because the prohibition to regular Jews remains indefinitely), but if the child is a female, שדיא אבתרה דידה – cast her after [her mother], because for a female, the Egyptian parent is the greater blemish (because a female Ammonite is permitted to regular Jews).
- The source that kiddushin are ineffective for prohibitions with a kares liability
The Gemara provides the source that kiddushin is ineffective between those prohibited with a punishment of kares: The passuk states regarding a divorcee: ויצאה מביתו והלכה והיתה לאיש אחר – and she leaves his house, and goes and becomes a wife for another man, implying: לאחרים ולא לקרובים – she can become married to a strange man, but not to relatives. The Gemara eventually asks that perhaps this only refers to אחות אשה – a wife’s sister, about whom the Torah wrote "לא תקח" – you shall not “take” (connoting marriage), and the above passuk teaches that kiddushin is not only prohibited, but ineffective. How is this extended to all relatives? The Gemara suggests they can be derived from אחות אשה, since they are all ervah, and carry the punishments of kares (for intentional violations) and chatas (for unintentional violations). However, two cases cannot be derived from a wife’s sister: אשת אח - a brother’s wife, which has the relative leniency of being permitted in a case of yibum (as opposed to a wife’s sister, who is prohibited even as a yevamah), and a married woman, who has the leniency of becoming permitted during her husband’s lifetime (through divorce).