Resources for Yevamos daf 21
1. The גמרא at the end of the last דף and the beginning of this דף brings the מחלוקת about ביאת כהן גדול באלמנה. The words the גמרא uses is “does it פּטור it’s צרה”. However, רש"י explains the גמרא to be referring to the אלמנה herself as well as her צרה. That means that according to רש"י there is a מחלוקת whether the אלמנה herself needs חליצה after the כהן גדול did יבום to her. The מהרש"א here is troubled by this since the גמרא should have said that the מחלוקת is about her and her צרה and not just mentioned צרה. Rather, the מהרש"א understood that everyone agrees that the אלמנה herself doesn’t need חליצה since קידושין are תופסין by אלמנה לכהן גדול. Even though it is true that there is no קיום מצוה since she is אסורה להתיבם מדאורייתא, nonetheless if the קידושין are תופסין it should mean she is כאשתו לכל דבר and just needs a גט. While רש"י clearly disagrees, this is in fact the opinion of the רמב"ם in הלכות יבום פּרק ו׳ הל׳ י"א who says that in the case where one did יבום to an אלמנה לכהן גדול one doesn’t have a “קנין גמור לפטור צרתה” which sounds like it is enough of a קנין in the אלמנה herself to פּטור her from חליצה. The קרני ראם asks a powerful and seemingly obvious question on the מהרש"א: if the מהרש"א is right and once קידושין are תופס the lady doesn’t need חליצה, what is the גמרא’s proof from the ברייתא that says "אם בעלו קנו"? We knew the קנין worked! Our question was whether that can exempt the צרה? There are several answers given by the אחרונים. The רש"ש answers very simply: if you look in the תוספתא that the גמרא is quoting you will see the next words are “ופּטרו את הצרות”. The רש"ש suggest that the printers just left off those words but the proof was from there.
2. The גמרא says that one is allowed to marry אשת חמיו (the (former) wife of one’s father in law). תוספות in ד"ה ומותר brings the ירושלמי that says it is אסור due to מראית עין. The ירושלמי also forbids stepchildren who grew up as brother and sister from marrying each other because of מראית עין as well. The בבלי in סוטה expressly disagrees with this ירושלמי and says there is no issue of מראית עין by stepchildren. There is a מחלוקת ראשונים about how to pasken these two questions that come from opposite extremes. ר"ת quoted by תוספות paskens like the ירושלמי and suggests that even though our גמרא does not mention any איסור by אשת חמיו it may have been prohibited at a later date. The רמב"ן says the גמרא in סוטה that disagrees with the premise of מראית עין by the stepchildren shows that the בבלי does not agree with the notion of מראית עין in these cases and both אשת חמיו and stepchildren are מותרות. The רא"ש in סימן א׳ says that it makes sense to him that the בבלי only argued by stepchildren since everyone knows they aren’t really related whereas אשת חמיו could be mistaken for חמותו. On the other extreme is the ריטב"א who in agreeing with the רמב"ן says that the בבלי allows both cases and the reason the גמרא only mentioned that there is no issue of מראית עין by stepchildren is because it is obvious that there is no מראית עין by אשת חמיו and it didn’t even need to be said!
3. The גמרא says that חז"ל forbade one to marry כלת בתו because of כלת בנו. The גמרא then brings three examples of people that had כלת בתו and כלת בנוs in one family. רש"י explains that since they are in one family they could be confused. What isn’t clear is what if they aren’t in one family? Is כלת בתו only אסור in cases where a כלת בנו exists in that family? The ריטב"א says explicitly that כלת בתו is only אסור when both are in one family and that is why the גמרא bothered listing examples of cases of people in their time who had both in one family—to teach you that only in those cases is it אסור. The מאירי disagrees and says that חז"ל forbade all כלת בתוs because of those cases. The ריטב"א himself asks תוספות’s question why כלת בתו isn’t forbidden because of the rule of “כל שבנקבה ערוה בזכר גזרו על אשתו”? He agrees with תוספות’s answer that it became אסור later. According to that, it should come out that everyone agrees that at this point כלת בתו is אסור in all circumstances because of the rule of כל שבנקבה. The ישועות יעקב in סימן ט"ו ס"ק ד makes this point להלכה (although not in relation to the ריטב"א).
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