Hilchos Bikkurim 1:1

There are 24 different gifts that are given to kohanim, all of them explicit in the Torah and all of them part of a covenant with Aaron. If a kohein doesn’t acknowledge the priestly service, he doesn’t have a share in the priesthood and doesn’t receive these gifts.

Hilchos Bikkurim 1:2

Every kohein who eats from one of these gifts that is considered holy (such as terumah) recites a blessing that Hashem “sanctified us with the holiness of Aaron and commanded us to eat such-and-such.”