Commentary for Kiddushin 105:28

So now we have a dispute about whether there is a dispute. Those rabbis sure love their disputes!

Abaye is now going to quote a long baraita that in its totality supports R. Yohanan. The details of this baraita are not relevant for our sugya, but I will still, of course, explain them briefly. The main message of the baraita is that the priests may not exchange one sacrificial gift (meat, fowl or meal-offering) for another.
Priests who receive meal-offerings as part of their portions may not demand to exchange them for sacrificial meat.

Abaye is now going to quote a long baraita that in its totality supports R. Yohanan. The details of this baraita are not relevant for our sugya, but I will still, of course, explain them briefly. The main message of the baraita is that the priests may not exchange one sacrificial gift (meat, fowl or meal-offering) for another.
Priests who receive meal-offerings as part of their portions may not demand to exchange them for sacrificial meat.

Meal-offerings can take the place of bird offerings for the poor—if the poor cannot afford a bird offering, they can bring a meal-offering. Therefore, I might have thought that they are exchangeable. They are not.

Animal sacrifices may also not be exchanged for bird sacrifices even though both are types of blood.

Fowl offerings are killed by pinching off their necks, whereas animal sacrifices are slaughtered with a knife. Thus one may not exchange one for the other. But meal offerings are all made with utensils. So maybe priests could exchange one meal-offering for another. They may not.

Even the same type of meal-offering may not be apportioned one in exchange for the other.

The same rules apply for all types of sacrifices—higher and lower ones. The thanksgiving offering is a sacrifice of lower sanctity.

The baraita now concludes by saying that priests with blemishes receives sacrificial portions, but not minors.
The entire prohibition of exchanging one portion for another implies that a priest cannot use his portion for anything, even to betroth a woman. The Sifra is the midrash on Leviticus, and the Talmud assumes its author is R. Judah. Thus, R. Judah does not believe that a priest can use his portion, whereas earlier he said that he can. We can assume that he retracted his opinion and that no one holds that a priest may use his portion to betroth a woman. This accords with R. Yohanan and opposes Ravץ

Rava cites a baraita that supports Rav. The baraita refers to priests dividing up the weekly showbread. The modest ones did not even want to eat it. Perhaps they felt it was too holy. In their place, the gluttonous ones take all of the shares. This seems to imply that they can exchange their portions—the modest ones do not take and in their place others do.

The Talmud rejects this meaning of “shared.” The gluttonous did not share their portions, they snatched, i.e. stole, them from one another. Those greedy priests!

The amoraim provide biblical verses to explain the meaning of Ben Hamtzan—son of the snatcher. You really don’t want to be called “son of the snatcher!”

R. Aha provides a verse to support R. Meir’s view that one cannot use second tithe to betroth a woman. Second tithe is holy to God; it cannot be used for betrothal.

One can use terumah for betrothal because the Torah does not say “to the Lord.” It says “of the Lord.” Yup, this is a bit of a nitpicky one.

Even though hallah, dough given to the priest, is described as “to the Lord” one can use it for betrothal because it is not called “holy” by the Torah. [Hallah is sometimes called terumah, because both are given to the priest].

One can use sabbatical year produce to betroth a woman because the Torah does not describe it as “to the Lord.”

When Jeremiah uses the words “to the Lord” and “holy” he is referring to Israel, not to terumah.
The Talmud then asks if Israel is holy to the Lord then why shouldn’t terumah also be holy to the Lord, and not usable as betrothal money. After all, the two are compared.
Rabin now pulls out another element of the verse about tithe—tithes are “for the Lord” and must remain in their natural form. They cannot be used for betrothal.