Resources for Yevamos daf 24
1. The משנה says that someone should not marry a spouse who converted for what seems to be ulterior motives. רבי נחמיה says that if someone converts for ulterior motives it is מעכב the גירות. However, רב says that it is still considered a good גירות. Nonetheless, ideally one should not marry this person because of “לזות שפתים”. There is a מחלוקת ראשונים what the לזות שפתים refers to which is fundamental to how we understand what was meant when רב said that we pasken that the conversions are really all valid. רש"י learns that the לזות שפתים refers to the fact that if they get married, people will say that the original קול was true and the two people really had been מזנה prior to the conversion and marriage. However, the רמב"ן, רשב"א, וריטב"א learn that the לזות שפתים is that it will look like the conversion really was for ulterior motives. The ריטב"א explains that it is only an issue of לזות שפתים and not מעיקר הדין since we can assume that not in spite of but rather because of the ulterior motives, they were forced to make a true קבלה. The אחיעזר in אבן העזר סימן כ"ו points out that this means that if we knew that the person wasn’t really מגייר בלב שלם, then the גירות would in fact be invalid. He also quotes the רמב"ם inהלכות איסורי ביאה פּרק י"ג הל׳ ט"ו who says that while we would not לכתחילה accept גרים who we knew were becoming גרים for ulterior motives, if they were מגייר we would assume their גירות was good but be “חוששין להם”. It sounds like if we were to somehow know that they were not מגייר בלב שלם then the גירות would not be חל. There is an important גמרא in שבת דף ל"א which is brought in תוספות ד"ה לא about someone who would only convert on condition he become a כהן גדול and הלל converted him. תוספות explains that הלל was confident that the man would eventually have a לב שלם. The simple reading of the גמרא is that he became a convert immediately. If so, how was the conversion valid in the meantime if we know it wasn’t בלב שלם now? The מהרש"א in the גמרא in שבת says that you must say that the גמרא just meant that הלל started the conversion process but didn’t actually convert them until later. The מהרש"א then asks an important question: if so, how did הלל teach him תורה? One isn’t allowed to teach תורה to a נכרי? He answers with an important חידוש quoted by many: since he was studying to become a גר and in the גירות process, he was therefore allowed to learn תורה even at that point.
2. The משנה says that it is a מצוה בגדול ליבם. However, if a younger brother does the מצוה it is valid מצות יבום. There is a famous ריטב"א in סוכה דף י"א ע"ב who says there is no such thing as something being a דין דאורייתא and having לכתחילה and בדיעבד. His example there is that if you say לולב צריך אגד is only למצוה and not מעכב, it must only be a דין דרבנן. If so, how would the ריטב"א understand our גמרא which seems to have a דין לכתחילה of מצוה בגדול לייבם but it isn’t מעכב?. One possibility suggested by רב יונתן זקס שליט"א is that מצוה בגדול is just a דין קדימה, meaning that the מצוה is מוטל עליו to do but it isn’t part of the מצוה itself.
3. The גמרא asks that perhaps if there is no בכור then there is no requirement for the oldest remaining brother to be the one to doיבום . The גמרא proves otherwise by quoting אביי קשישא that says that if the גדול doesn’t want to do יבום, they go to the next youngest one, and keep going down. This means that the חיוב goes by age order and each consecutive brother becomes next in line for the מצוה. That is the גירסא of רש"י. Theרמב"ם in in הלכות יבום פּרק ב׳ הל׳ ז׳ וי"ב argues on רש"י and says that if the oldest brother doesn’t want to do יבום then the remaining brothers have the exact same level of חיוב to doיבום . This is based on an alternate גירסא in אביי קשישא (which other ראשונים had) which says if the גדול doesn’t want to doיבום they just “ask the other brothers”. This just sounds like if the oldest doesn’t want to do יבום , all the other brothers are exactly equal in their חיוב. The question on theרמב"ם is that those are also the exact words of the משנה on דף ל"ט. If so, it begs the question why the גמרא quoted אביי קשישא when it could have brought a משנה? רש"י himself inד"ה הולכין says that there is no proof from the משנה since “גדול” could mean בכור. However, if the רמב"ם had the correct גירסא, then there should have been a proof from that משנה since it’s the exact same words!? The לחם משנה explains that theרמב"ם must have learned that while one can be מדחיק the words of a משנה that way, a ברייתא wouldn’t have been so סתום and non-specific.
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