Charles Ellicott Commentary Leviticus 8:23

"And he slew it; and Moses took of the blood thereof, and put it upon the tip of Aaron`s right ear, and upon the thumb of his right hand, and upon the great toe of his right foot." — Leviticus 8:23 (ASV)

And he slew it. — Better, and he killed, as the same word is rendered in the Authorised Version in Leviticus 8:19; that is, Moses killed it.

And put it upon the tip of Aaron’s right ear. — To teach him that, as the mediator between God and His people, it was his solemn duty to diligently listen to the commandments of the Lord.

And upon the thumb of his right hand. — To remind him that from now on he is to execute God’s will and walk in the way of His commandments.