Resources for Yevamos daf 89
1. The גמרא discusses how we know הפקר ב"ד הפקר and gives two possible פּסוקים in נ"ך to prove it. There is a מחלוקת ראשונים as to whether הפקר ב"ד הפקר gives ב"ד the power to take away from one person and give it to another person or if it just gives ב"ד the ability to take it away from someone and make it הפקר (as the words sound) but doesn’t give them the power to give it to someone else. רבינו יונה in עליות דר׳ יונה ב"ב דף נ"ד ע"ב says that ב"ד can only take away from someone but you require someone else to be מקנה it to a second person. רש"י in גיטין דף ך ד"ה אקנויי as well as the רשב"א in גיטין דף ל"ו ע"ב says that ב"ד does have the power to be מקנה it to another person. An interesting נפקא מינה between these two opinions is regarding making a קנין דרבנן for a דין דאורייתא. For example, if you were קונה your לולב with a קנין דרבנן, perhaps you aren’t יוצא your חיוב דאורייתא. The שו"ת חתם סופר in או"ח סימן קי"ז בסוף explains that if you hold הפקר ב"ד הפקר helps to be מקנה something to someone else, then even if it is a קנין דרבנן you would still be קונה מדאורייתא because the concept of הפקר ב"ד הפקר is a דאורייתא concept. However, if הפקר ב"ד הפקר can only be מפקיר something, then מדאורייתא it isn’t your לולב. A notable exception to this is חמץ בפּסח. In that case, if you do a קנין דרבנן with the נכרי it definitely works דאורייתא since it that case you only need for it to be הפקר for it to have succeeded in getting the ישראל out of בל יראה. The ים של שלמה in פּרק י סימן י"ט says that the מחלוקת as to whether הפקר ב"ד הפקר allows ב"ד to be מקנה or if it only allows them to be מפקיר is directly תלוי on the מחלוקת in our גמרא as to which פּסוק you learn הפקר ב"ד הפקר from. If you learn it from the פּסוק in עזרא as ר׳ יצחק did, then that פּסוק only says “יחרם כל רכושו” which would just mean its הפקר. However, if you learn it from the פּסוק in יהושע as ר׳ אלעזר did, that פּסוק is talking about giving נחלות to people so that would teach you that ב"ד can even give it to others.
2. The גמרא says that when one is מפריש the תרומות ומעשרות from squash and watermelon they need to taste it before they are מפריש it since it often goes bad. תוספות in ד"ה איבעי says that you would still need to be מתקן a small amount of תרומות ומעשרות so that you would be able to taste it because otherwise the food is טבל so how could you taste it? The ישרש יעקב asks the following: the צמח צדק in סימן מ"ז says that even though the ריב"ש writes in סימן רפּ"ח that there is an איסור דרבנן to taste non-kosher food and spit it out, you are allowed to taste an איסור דרבנן and spit it out since it is a גזרה לגזרה (tasting treif is an איסור דרבנן lest you swallow it and here the איסור itself is דרבנן). The ישרש יעקב asks that our תוספות here is talking about an איסור דרבנן since the חיוב תרומות ומעשרות on vegetables is only a חיוב דרבנן, and yet it is clearl from תוספות that you are not allowed to taste it! He answers that even though the ריב"ש writes that it is only an איסור דרבנן to taste non-kosher food if you don’t swallow it, if it is אסור בהנאה then it is an איסור דאורייתא since you get הנאה even by tasting it. Our תוספות is discussing טבל which is אסור בהנאה של כילוי (benefit where you ruin it by using it). Therefore, when you taste food and spit it out it is a הנאה של כילוי. If so, it is מסתבר that everyone would agree that you can’t taste an איסור דרבנן where it is אסור בהנאה.
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