- אלו הן הנסקלין
The next Mishnah states: אלו הן הנסקלין – these are the ones who are stoned (totaling eighteen): one who has relations with his mother, or his father’s wife, or his daughter-in-law, or with a male, or an animal, or a woman who brings an animal upon herself; a מגדף – blasphemer, one who worships עבודה זרה, one who gives of his children to מולך, one who performs אוב or ידעוני (different methods of speaking to the dead, described on Daf 65a), one who desecrates Shabbos, one who curses his parent, one who has relations with a נערה מאורסה, a מסית – one who instigates someone to idolatry, a מדיח – one who leads an entire city astray to idolatry, and בן סורר ומורה – a wayward and rebellious son (discussed in the eighth Perek). If one has relations with his mother who was married to his father, חייב עליה משום אם ומשום אשת אב – he is liable both for relations with a mother and for relations with a father’s wife; thus, if it was בשוגג, he brings two חטאות. Rebbe Yehudah says he is only liable for אמו, as the Gemara will explain. The Mishnah gives more examples of relations carrying two prohibitions.
- Rebbe Yehudah of the Baraisa: a mother who is prohibited to his father with a לאו is not אשת אביו
A Baraisa records a different version of Rebbe Yehudah’s opinion: אם לא היתה אמו ראויה לאביו – if his mother was not fit for his father, her marriage to his father was ineffective, אינו חייב אלא משום האם בלבד - and he is only liable for relations with a mother, not for a father’s wife. This cannot mean the mother was prohibited to the father with an aveirah punishable by kares or מיתת בית דין, because the Rabbonon agree such a marriage is ineffective. Rather, Rebbe Yehudah is discussing where his mother is prohibited to his father with an ordinary לאו, and Rebbe Yehudah holds like Rebbe Akiva, that אין קידושין תופסין בחייבי לאוין – kiddushin does not take effect with those prohibited by a לאו. The Gemara adds that just as a יבמה who is forbidden to the יבם with kares is exempt from yibum or chalitzah, Rebbe Yehudah would hold the same applies to a יבמה who is forbidden to the יבם with a mere לאו, since he holds kiddushin would not be effective between them.
- Rebbe Yehudah’s source that relations with אמו is not also liable for אשת אביו
In the Mishnah, Rebbe Yehudah taught that one who has relations with his mother who was also his father’s wife is only liable for אמו, but not for אשת אביו. Abaye explains the source is the phrase "אמך היא" – she is your mother, teaching: משום אמו אתה מחייבו – you may make him liable for relations with his mother, ואי אתה מחייבו משום אשת אב – but you may not make him liable for relations with his father’s wife. The Gemara objects that the opposite derashah should be made from the next passuk, which says "ערות אביך היא" – it is your father’s nakedness, teaching that for relations with his father’s wife who is also his mother, he is not liable for אמו. The result of these opposing derashos would be that for such relations, there is no liability at all!? A second answer is attempted but rejected. Rava therefore defends Abaye’s answer: Rebbe Yehudah, based on a gezeirah shavah, interprets "ערות אביך" at the beginning of the first passuk to mean a father’s wife (unlike the Rabbonon, who interpret it literally to mean his father). This would imply that a father’s wife liability includes when she is his mother, and so "אמך היא" is darshened to exclude a mother from liability for אשת אביו.