Charles Ellicott Commentary Exodus 29:25

"And thou shalt take them from their hands, and burn them on the altar upon the burnt-offering, for a sweet savor before Jehovah: it is an offering made by fire unto Jehovah." — Exodus 29:25 (ASV)

Thou shalt receive them ... and burn them. —On conferring his priestly functions to his brother and his brother's sons, Moses was not immediately to lay them aside; but, as he had begun the consecration ceremony, so he was to complete it. (Compare to Exodus 29:31-37 and Leviticus 8:28-36.)