Resources for Yevamos daf 34

1.      The גמרא says according to רש"י that we can have a case of בת אחת of the various עריות by having a שליח be מקבל קידושין for the male children to be given over to the female children with the intention for it be חל the next day when they are both considered adults. תוספות in ד"ה מתוך asks that children cant make a שליח nor can they make קידושין so this could occur once they have already turned 13. The ריטב"א asks on רש"י in a different way. The ריטב"א asks that if the children gave the קידושין to be חל in the future then it is a דבר שלא בא לעולם which can’t be קונה! It doesn’t seem like the ריטב"א is concerned with תוספות’s issue that a child’s מעשה קידושין is not valid. The קובץ הערות in סימן כ"ט אות ה says a tremendous חידוש. He explains that both רש"י and the ריטב"א hold that the fact that a child can’t do a מעשה קנין is only a גזרת הכתוב but in principle there is nothing wrong with his מעשה קנין. Therefore, if the קנין is done by a child on behalf of a גדול, it works. In שיעורי ר׳ שמואל he says a similar idea: it’s not that a child who is 12.5 years old has no דעת. Rather, it doesn’t have a דין of דעת. Therefore, even if the child wasn’t thinking anything when he turned 13, the original דעת he had when was 12.5 is now valid and the קידושין works.

2.      The גמרא says that according to ר׳ מאיר one could be חייב on שבת which falls on יום הכיפּורים for eating and הוצאה because the איסורים are חל בבת אחת. The way that happens is that one puts it in his mouth in his house but doesn’t swallow it until he is in רשות הרבים. Therefore, the הנחה and גמר אכילה happen at the same instant—when he swallows it. There is a fascinating חתם סופר in או"ח סימן קי"ז who says that that since the גמרא in יומא says that the שיעור to be חייב on אכילה ביוה"כ is a ככותבת because that is the שיעור ליתבי דעתיה(to feel somewhat satiated), that means the שיעור isתלוי  on הנאת מעיו and not the enjoyment of the taste. That means the חיוב should only be once it reaches your insides and you feel full and not the second you swallow it. If so, that would mean the חיוב הוצאה happens when you swallow it (as that is considered הנחה) and the חיוב אכילה comes later when it is in your מעיים in which case it is not בבת אחת. That would seem to be against our גמרא. The אבני נזר in או"ח סימן קכ"ג answers that notwithstanding the חתם סופר‘s חידוש, the swallowing is still a part of the איסור and that happens when the הוצאה occurs as well.

There is another fascinating אבני נזר about the above גמרא. The אבני נזר inאו"ח סימן רמ"ה asks why isn’t carrying food in רשות הרבים a מלאכה שאינה צריכה לגופה? After all, it’s not that you need the food outside, you just need it where you are. This is similar to the case in the beginning of שבת of the זב who carries a כיס on his person wherever he goes to catch his זיבות where we call it a מלאכה שאינה צריכה לגופה since he doesn’t need it outside but rather just with him. The אבני נזר proves from this question a big יסוד: it is only the עקירה והנחה that makes the חיוב שבת and the changing רשויות is just a תנאי in the מלאכה. So when you picked up the food, you needed it up so you could eat it, and when you swallowed it you need it there too. The only thing you didn’t need is the moving to a different רשות. That’s enough to be חייב. However, by the case of the זב, you need to pick it up to put it on but you didn’t need to take it off or stop walking so it is not חייב.