Exodus 29:24 - Ellicott's Commentary On The Whole Bible

Thou shalt put all in the hands of Aaron, and in the hands of his sons. — Rather, on the hands. Having placed the offerings on the hands of his brother and his brother’s sons, Moses was to put his own hands beneath theirs, and to make a waving motion towards the four quarters of the sky, thus presenting the offerings to the ubiquitous God. Aaron and his sons thus performed their first priestly act, as passive instruments in Moses’ hands, by his muscular energy. Their priestly character was by these means made complete. (On “wave offerings,” see Note upon Leviticus 7:30.)