Rashi on Exodus 29:24/רש"י על שמות כ״ט:כ״ד

1על 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.

2תנופה A WAVE OFFERING — He moved it about horizontally in all directions to the glory of Him to Whom belong the four quarters of the world. This waving was symbolical of preventing and making of none effect misfortune and destructive winds. Then he moved it upwards and downward to the glory of Him to Whom belong heaven and earth and this was symbolical of keeping away injurious dews (Menachot 62a).