Resources for Yevamos daf 42
1. The גמרא says that a woman must wait three months after she was last married until she marries a new husband. שמואל says the reason is הבחנה and brings the פּסוק of להיות לך לאלקים ולזרעך אחריך וכו׳. The קרן אורה in ד"ה אלא says that he thinks that even according to שמואל it is only an אסמכתא דרבנן and not a real דין דאורייתא. He also says that even if you would argue that knowing the יחוס of a child is a דין דאורייתא, the איסור הבחנה is only דרבנן since מן התורה we would say you can go בתר רוב and in most cases it will be obvious whose child it is. The ערוך לנר in ד"ה ברש"י ד"ה ולזרעך understands that according to שמואל it is a דין דאורייתא. He points out that the תרגום יונתן בן עוזיאל and ספרי in פּרשת כי תצא say the reason a יפת תואר must wait before she can be brought into the Yid’s house is because of הבחנה which also makes it sound like it is a דין דאורייתא.
2. The גמרא says that one may not marry מעוברת ומינקת חברו. The מסקנא of the גמרא is that the reason one cannot marry these women is that she may get pregnant which will hurt her milk and her husband may not want to pay for the extra nourishment she will need for the baby. Theרמב"ם in הלכות גירושין פּרק י"א הל׳ כ"ה says that the reason that you can’t marry מעוברת חבירו is because you may hurt the baby during תשמיש. The כסף משנה there asks on the רמב"ם that the גמרא rejected that answer because if it were true then a person couldn’t stay married to their own pregnant wife! He concludes that it must be that theרמב"ם had a different גירסא, and in his גירסא it didn’t say the word "אלא". In other words, the answer of “hurting the child during “תשמיש wasn’t completely rejected. Rather, the גמרא was just giving an answer that aligned with the assumption of the questioner since the answer needed to be said for מינקת anyway. Nonethless, the גמרא could have answered that a person is more careful with their own children than someone else’s. As to why theרמב"ם picked this reason and not the one the גמרא gives, he brings the מהרי"ק that this answer includes more women such as a woman who isn’t going to nurse anyway but may have issues with their child’s safety.
3. תוספות in ד"ה סתם brings a מחלוקת ראשונים whether the איסור of מינקת חבירו is only by an אלמנה or whether it also applies to a גרושה. The ר"ש הזקן says it doesn’t apply to a גרושה since she has no שיעבוד to nurse the child anyway, as opposed to an אלמנה who does. ר"ת and the שאילתות disagree and say the איסור applies to both אלמנה and גרושה. The נודע ביהודה in אה"ע סימן י"ז says that all the פּוסקים disagree with the ר"ש הזקן but he thinks that it depends on the case. He says that our גמרא is almost identical to the גמרא in כתובות on דף ס׳ although there are a few critical differences. Our גמרא says לא ישא מעוברת חברו which means there is an איסור on the man to marry her whereas in כתובות it says מניקה לא תנשא לאחר מיתת בעלה עד כ"ד חדש which means she can’t marry him. The גמרא in כתובות also mentions her husband’s death as well as a time limit of 24 months whereas our גמרא doesn’t mention either. To answer this apparent contradiction he says that our גמרא is focusing on the man and discussing both a widow and a גרושה. The man can’t marry her because מסתמא she will nurse her child. It also doesn’t give a timeline because as long as she is nursing there is an איסור for him to marry her lest milk become נעכר. However, from her perspective, if she is a גרושה she can decide that she may not want to nurse the child. In that case she can get married. However, the גמרא in כתובות is discussing an אלמנה where she has no right to not nurse the child in which case she cant get married for 24 months. So he disagrees with the ר"ש הזקן by a גרושה who is actually nursing but thinks he is right if she is not in fact being מניק. Based on this, he allowed a גרושה to remarry within 24 months if she wasn’t planning on nursing. The שבט הלוי in חלק י סימן רל"ב relied on this נודע ביהודה in a שעת הדחק.
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