Yevamot — Daf 9b

דפליגי ר"ש ורבנן וקתני בנולד

ולבסוף ייבם לא פליג ר"ש

והאמר ר' אושעיא חלוק היה ר"ש אף בראשונה

הא איתותב ר' אושעיא

והאמר רב יהודה אמר רב וכן תני ר' חייא בכולן אני קורא בהן האסורה לזה מותרת לזה והאסורה לזה מותרת לזה ואחותה שהיא יבמתה חולצת או מתייבמת

ורב יהודה מתרגם מחמותו ואילך אבל שיתא בבי דרישא לא מ"ט

כיון דבתו

באונסין משכחת בנשואין לא משכחת לה בנשואין קמיירי באונסין לא קא מיירי

ואביי מתרגם אף בתו מאנוסתו כיון דאשכוחי משכחת לה אי בעיא מן האונסין תהוי [אי בעיא מן הנשואין תהוי] אבל אשת אחיו שלא היה בעולמו לא מאי טעמא

כיון דלר"ש הוא דמשכחת לה לרבנן לא משכחת לה בפלוגתא לא קא מיירי

ורב ספרא מתרגם אף אשת אחיו שלא היה בעולמו ומשכחת לה בשיתא אחים ואליבא דר' שמעון

concerning which R. Simeon and the Rabbis are in dispute,  and which is nevertheless mentioned? — R. Simeon does not dispute the case where the birth  was first, and the levirate marriage  later.  Did not R. Oshaia, however, say  that R. Simeon disputed the first case also?  — Surely. R. Oshaia's view was refuted. Did not, however, Rab Judah state in the name of Rab, and R. Hiyya also taught: In the case of all these  it may happen that she who is forbidden to one brother may be permitted to the other  while she who is forbidden to the other brother may be permitted to the one, and that her sister who is her sister-in-law may be subject either to halizah or to the levirate marriage.  And Rab Judah interpreted [it  as referring to those]  from one's MOTHER-IN-LAW onwards but not to the first six categories. What is the reason? Because in the case of a daughter this  is possible only [with one born] from a woman who had been outraged but not [with one born] from a legal marriage,  [and the author of our Mishnah] deals only with cases of legal matrimony and not with those of outraged women.  And Abaye interpreted it  [as referring] also to a daughter from a woman who had been out raged, because, since [the application of Rab's statement] is quite possible in her case, it matters not whether she was born from a woman who was legally married or from one that had been outraged; but not to the wife of a brother who was not his contemporary. What is the reason? Because [the application of Rab's statement in this case] is possible only according to the view of R. Simeon and not according to that of the Rabbis, [the author of our Mishnah] does not deal with any matter which is in dispute. And R. Safra interprets it  as referring also to the wife of a brother who was not his contemporary, and [in his opinion] it  is possible in the case of six brothers in accordance with the view of R. Simeon.