Midrasch zu Shekalim 4:10

That they take for me an offering (Exod. 25:2). May it please our masters to teach us: What did they do with the surplus offering?¹The surplus offering was from the funds contributed for the building of the Sanctuary (M. Shekalim 4:4). Thus did our masters teach us: They fashioned with it the hammered gold overlay for the Holy of Holies. You find that the Holy One, blessed be He, chose two offerings (terumot): the offering (set aside) for the building of the Tabernacle and the priestly offering. The priestly offering (was given to them) in order that they become students of the law.²These offerings increased their opportunity to study the law. The midrash compares these offerings because both are called terumah. R. Yannai said: Any priest who is not a student of the law, it is permitted to eat the offering on his grave.³Etz Joseph suggests that an ignorant priest would even permit eating the terumah offering, which must be maintained in a state of ritual purity, in a cemetery, from which priests are generally barred. The intent may be that the priest, in his ignorance, probably collected his dues improperly, and so it is really common, and thus may be consumed even on his (i.e., the ignorant priest’s) grave, since he is worthy of death.