Resources for Nedarim 33
The גמרא says that when someone says הנאת מאכלך עלי it would make it that you couldn’t use that person’s moistened wheat to rub on a wound. רבי עקיבא איגר in יו"ד סימן רכ"אpoints out that that type of הנאה is obviously a הנאה שלא כדרכה yet the גמרא clearly says it is אסור. This would seem to be a proof against the מגן אברהםin או"ח סימן שפּ"ו ס"ק י who says regarding עירוב תחומין that you can use bread that someone was מדיר you from for your עירובsince people who are מדיר others don’t mean to be מדיר them from הנאה שלא כדרכה. The חידושי חתם סופר answers for the מגן אברהם that when you אסור someone on your food, that person cant eat it nor can he get normal הנאה like smelling hot bread. However, he can get הנאה שלא כדרכה like the מג"א said. However, in our גמרא the person specifically said הנאת מאכלך עלי which sounds like he is adding additional הנאות and that would include even שלא כדרך הנאתה What is interesting to me is that the שולחן ערוך in רכ"א sounds like if you אסור someone on food they can get הנאה from it and just cant eat it. Perhaps it is לאו דוקה.
The משנהsays that if you are מודר הנאה from someone they are still allowed to pay their מחצית השקל, pay back their loan, and return their אבדה with the condition that if people typically reimburse the משיב for his efforts that the money be given to הקדש. The גמרא here explains that the reason it is allowed is because it is just אברוחי ארי בעלמא. At first glance that היתר seems quite broad. Are there any limits? The first limit we see is mentioned by the ר"ן regarding the money one must give to הקדש when someone returned their lost item. The ר"ן says one cannot simply be מוחל the משיב אבדה since that would be giving him direct הנאה. One could ask on the ר"ן: isn’t that just אברוחי ארי as well? We see from the ר"ן that one cannot be מהנה the מודר directly. Rather, the היתר of אברוחי ארי is only indirectly. Further, תוספות here asks why is it that in בבא מציעא דף צ"ג ע"ב it says that if you fight off a lion from someone’s animals you can demand payment. Isn’t that literally אברוחי ארי? תוספות answers with a big יסוד: if it’s ברי היזיקא then that’s called הנאה even according to חנן and you can charge for it. However, if it just might happen then you can’t demand payment and its not הנאה according to חנן. By our case, it is possible that you could have convinced the lender to be מוחל the loan so it’s not considered ברי הזיקא. If so, we should have an issue by שוקל לו את שקלו because there it is ברי הזיקא since you can’t convince the גזבר to be מוחל you (this is what the ר"ן here ד"ה לענין הלכה asks on תוספות). One possibility to answer this is the גמראin כתובות דף ק"ח ע"א. There the גמרא quotes our משנה and says there is no issue by שוקל לו את שקלו since מצוה קעביד. The simple understanding of that is that donating to the בית המקדש is a מצוה. Therefore, as the רשב"א explains in דף ל"ד ד"ה לא, it is considered that the person is simply being מתעסק במצוה and the benefit is just ממילא. The תוספות רי"ד there in כתובות actually doesn’t have the גירסא of מצוה קעביד by שוקל את שקלו, presumably because it is a stretch to say it is a מצוה to pay someone else’s שקל obligation. Rather, he would likely have learned like the ר"ן that even if there is no way out it’s still not considered הנאה.
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