Commento su Esodo 29:24

על כפי אהרן … והנפת [AND THOU SHALT PUT ALL] IN THE HANDS OF AARON … AND THOU SHALT WAVE THEM — The rule is that both of them take part in the waving ceremony, the “owner” and the priest. How is this done? The priest places his hand beneath the “owner’s” hand, and thus does the waving (Menachot 61b) — and in case of this offering Aaron and his sons were the “owners” and Moses the priest, and therefore Scripture enacts as stated here.

והנפת, this “waving” applies to the part of the sacrificial animal that the priests are given to eat. The main reason is that the priest should remain aware that he eats from שלחן גבוה, “from G’d’s table,” so to speak, i.e. that his portions are a “kick back,” totally voluntary gift from G’d, and that he does not eat by “rights,” i.e. that this is what the owner of the sacrificial animal designated for him. In this instance, also the part of the animal which would normally be his to eat wound up on the altar instead of being consumed by the priests, it being an introductory symbolic procedure. [perhaps similar to the concept of ראשית, the “first” part of crops which need to be consecrated to G’d of produce originating from the earth. Ed.]

Both participated in the waving. . . [Rashi knows this] because it is written, “Place all these things upon the hands of Aharon. . . and you shall wave them.” If they are on Aharon’s hands, how could Moshe wave them? Yet it is written, “You shall wave them.” Perforce, they both waved.