Rashi on Numbers 8:20/רש"י על במדבר ח׳:כ׳

1ויעש משה ואהרן וכל עדת וגו׳ AND MOSES AND AARON AND ALL THE CONGREGATION … DID [TO THE LEVITES ACCORDING UNTO ALL THAT THE LORD COMMANDED MOSES] — i.e. Moses presented them (v. 13), Aaron made the waving with them (v. 11) and the Israelites put their hands (v. 10) upon the Levites’ heads (cf., however, Ibn Ezra).