Resources for Kesubos daf 58

1.     The גמרא on דף נ"ז ע"ב said in the name of עולא that מדאורייתא an ארוסה can eat תרומה as it says וכהן כי יקנה נפש קנין כספּו. The גמרא on our דף says that a יבם cannot be מאכיל his wife תרומה since it isn’t his קנין כספּו but rather his brother’s. רש"י in דף נ"ז ד"ה עשתה seems to understand that the יבם not being able to give the יבמה her תרומה is aדין דאורייתא. רש"י on  דף נ"ח ד"ה והאי clarifies that our גמרא is referring to prior to יבום being done. However, once יבום is done the husband can give her תרומה since she is fully the יבם’s wife. We would have expected רש"י to end there. However, רש"י goes on to explain that even though there was no קנין כסף done by יבום, the קנין of ביאה works by a regular lady (as all קניני אישות are הוקש  to each other) so it should work by a יבמה  as well. There are many questions on all of this. First, why would a יבם not be able to be מאכיל his יבמה her תרומה? After all, a יבם is able to be מפיר נדריה so we see a יבם has דיני דאורייתא. In fact, תוספות in ד"ה ואפילו says the יבם can be מאכיל her תרומה מדאורייתא. Furthermore, why would רש"י feel the need to explain why after יבום she can eat תרומה based on it being similar to קידושי ביאה? Isn’t it פּשוט that a כהן can be מאכיל his wife תרומה?! The אבני מילואים in his שו"ת in סימן י"ז has a long, famous, and incredibly yesodosdik piece on the entire nature of a כהן being מאכיל תרומה to anyone. The עיקר נקודה is the following: there are two type of קנינים. There are קניני ממון and קניני איסור. A כהן can feed his wife, עבד כנעני, and animal, תרומה. He has a ממון קנין in his animal and עבד. However, he has no קנין ממון in his wife at all. After all, she can say to him איני ניזונית ואיני עושה. All he has in her is קניני איסור which does not allow her to marry anyone else. The אבני מילואים says that תרומה follows קניני איסור and not קניני ממון. The proof is that if a person is מפקיר their עבד but doesn’t give them a גט שחרור they can still eat תרומה. In that case they have removed their קנין ממון  left but the קנין איסור  remains. You see from there that the קנין ממון is what drives the ability to eat תרומה. This explains why a man can give his wife and עבד their תרומה, but does not explain why a כהן can give his animal תרומה in which he has no קנין איסור whatsoever. The אבני מילואים explains that you only need a קנין איסור if you are שייך to a קנין איסור. However, if you are only שייך to a קנין ממון then that’s all you need. The other question is how any of this fits the words of the פּסוק "קנין כספּו"? The אבני מילואים brings the שיטה מקובצת who explains that the קנין איסור must come about via כסף, so כסף קידושין works and the other קנינים work as well because of a היקש to קנין כסף. Based on this the אבני מילואים says we can explain our רש"י by a יבם. רש"י understood that since there is no כסף nor היקש to כסף by a יבם at all, he cannot be מאכיל his יבמה in תרומה מדאורייתא. However, once יבום is done, then we say we aren’t מחלק בין הביאות. (It should be noted that many of the ראשונים who hold the יבמה can eat תרומה מדאורייתא agree that it isn’t because of the יבם but rather because of the dead brother who had a full קנין.)