Albert Barnes Commentary Leviticus 9:22

"And Aaron lifted up his hands toward the people, and blessed them; and he came down from offering the sin-offering, and the burnt-offering, and the peace-offerings." — Leviticus 9:22 (ASV)

Aaron having completed the offerings, before he came down from the stage surrounding the altar on which the priests used to stand to officiate , turned toward the people, and blessed them; probably using the form which became the established one for the priests (Numbers 6:24–26), and which is still maintained in the synagogues.