Resources for Yevamos daf 66
1. The גמרא brings a ברייתא that says that a כהן that marries a woman or buys a slave can feed them תרומה as it says “וכהן כי יקנה נפש קנין כספּו”. The אבני מילואים in תשובות סימן י"ז has an important discussion as to why the wife of a כהן is called קנין כספּו. An עבד עברי doesn’t eat תרומה so why should she? Her מעשה ידים are her own מן התורה, so in what way does he own his wife? He answers with a יסוד: by an עבד כנעני there are two קנינים: a קנין ממון and a קנין איסור. The קנין ממון makes him yours financially. The קנין איסור makes it that he is חייב במצוות כאשה. By a wife, especially if you have only done אירוסין, one has no financial ownership of any kind. There is only a קנין איסור where you acquire her insofar as she is אסורה on everyone else as an אשת איש. When it comes to תרומה, the only קנין that is relevant is the קינן איסור. Therefore, a wife can eat תרומה but an עבד עברי can’t since a wife is a קנין איסור and an עבד עברי is only a קנין ממון. (The fact that an עבד עברי is מותר בשפחה he explains in the name of תוספות that it is based on his קנין ממון). Based on this he explains that the גמרא that the first תוספות in our פּרק brings that an עבד כנעני that the master made הפקר can still eat תרומה from his master is because even though his קנין ממון is gone, his קנין איסור still exists. As to why the animal of a כהן can eat תרומה even though there is obviously is no קנין איסור in that case, he adds another חידוש: if there isn’t a קנין איסור that could even possibly exist, then even a קנין ממון allows you to eat תרומה.
2. רב ספרא says that if a person has full אחריות on something such as animal where if it goes up and down in price he absorbs it, then he can give it תרומה. The ריטב"א asks what happened to the requirement for it to be קנין כספּו? He answers that the אחריות he has is a קנין כל דהו and for feeding someone תרומה, a קנין כל דהו is sufficient. However, in חידושי מרן רי"ז הלוי in the מכתבים in the back of the ספר on page ע"ט, the Brisker Rav says that the גמרא doesn’t mean that אחריות creates ownership. Rather, it is just מגלה that there some kind of ownership exists. In other words, by the fact that if the item goes down in price you must absorb the loss and if it goes up you keep the profit, it must be that you are a partial owner yourself. This has applications for many areas. One of them is טבילת כלים. There is a הלכה that if you have an item that requires טבילה but its שבת and you can’t be toveil it, you can give it to a נכרי as a present and ask him to lend it back to you. This way the vessel will be exempt from טבילה. The question is can you leave it that way forever or do you need to טובל it after שבת? Many אחרונים require it to be toveiled after שבתand are not happy with relying on this עצה permanently. One of the reasons sited by the שבט הלוי in חלק ט סימן קס"ז is our סוגיא that says if you have אחריות for something you are considered the owner. As such, the yid is really an owner as well.
3. The גמרא says that a כהן cannot give תרומה to the animal of a ישראל. תוספות in ד"ה לא asks what the issue with feeding the ישראל ‘s animal? If the כהן wants to give his תרומה to an animal, why would that be a problem? תרומה isn’t אסור בהנאה to a ישראל! He answers that תרומה is אסור בהנאה to a ישראל if it is a הנאה where the תרומה is destroyed in the process(הנאה של כילוי). There is a surprising opinion brought in the מרדכי in סימן ס"ו from רבינו יקר that says the issue is that a Jew may come to eat the animal that was fed with תרומה. The מרדכי asks on him that if so one could not eat chickens since they were fed with שרצים. תוספות ישנים in אות א brings a different answer. He says that there is no איסור for a for aישראל to benefit from תרומה . Rather, the issue here is that the animal can’t eatתרומה as it says “כהן כי יקנה נפש” and נפש includes an animal. (Obviously animals don’t have מצוות. What he means is that the כהן cant give a "נפש" any תרומה if he doesn’t own it).
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