Resources for Yevamos daf 28
מראה מקומות
1. The גמרא questions ר׳ יוחנן who says אחיות איני יודע מי שנאן and suggests that perhaps our משנה is discussing a case where two sisters fall to יבום to two brothers and they don’t know which one fell to יבום first. The גמרא says that if that were the case of our משנה then it would not have said אם קדמו וכנסו יוציאו. The reason it couldn’t have said that is because the second brother could claim that his wife is possibly מותרת to him because if the first brother happened to have done יבום to the יבמה who fell second, then his wife is מותרת since she is now הותרה, ונאסרה וחזרה והותרה. Because of this, ר׳ יוחנן is forced to say אחיות אינו יודע מי שנאן. רש"י in ד"ה בשלמא is implicitly bothered by a question: how does the גמרא know that we would allow them to stay married if the woman is still a ספק whether she is אסורה on the יבם? רש"י in explains that we know this from the משנה earlier on דף דף כ"ג ע"ב. The משנה over there discusses two men with two brothers each that are each מקדש one of two sisters and don’t remember which one they were מקדש and then they both die and their wives fall to יבום. If the first group of brothers both did חליצה and the second group of brothers both do יבום, we allow the second group to stay married even though one may be married to his אחות זקוקתו. רש"י there in ד"ה קדמו explains that the reason is because each married brother can say ממה נפשך: perhaps I got the woman who was the actual יבמה. Even if I didn’t and I married her sister who would be אחות זקוקתו, that איסור is gone at this point since my brother did יבום to the יבמה so she isn’t זקוקה anymore. רבי עקיבא איגר here asks how that could possibly be a proof to our סוגיא? In the case of דף כ"ג, the איסור of אחות זקוקתו is for sure gone. In our גמרא, if he got the wrong lady, then she is someone who was נאסרה וחזרה והותרה and she remains אסור forever! He leaves it צע"ג.
2. The גמרא says that ר"ש learns from the פּסוק of לצרור that if two sisters fall to יבום and become אחות זקוקתו, there is no יבום even מדאורייתא. There is an interesting חקירה in the אחרונים as to what the natures of this פּטור is: is it just a general פּטור from יבום like an איילונית or is it considered a real ערוה like אחות אשה? In רש"י ד"ה ליגזור, רש"י explains that the way it works is that the תורה exempted these women from יבום and חליצה and the איסור אשת אח comes back ממילא. That sounds like it’s just a פּטור in which case one would assume that while the sisters themselves are פּטורות they wouldn’t פּטור their צרות. However, the מאירי and the נימוקי יוסף in ד"ה פּוטר say that the sisters are considered a full ערוה of אחות אשה through זיקה. If the ערוה is אחות אשה then one would assume that the צרות would be פּטורות. In חידושי ר׳ נחום in אות תע"ה he brings a תוספות in קידושין דף נ׳ ע"ב who says that the כרת of אשת אח itself is what creates the פּטור in our case, unlike רש"י who said they are פּטור and therefore the אשת אח comes back. That sounds more like the אשת אח itself is a direct ערוה like אשת אחיו שלא היה בעולמו which would exempt a צרה.
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