Matthew Poole and continuators on Leviticus 9:22

22 And Aaron lift up his hand towards the people, and blessed them , and came down from offering of the sin-offering and the burnt-offering, and peace-offerings.

His right hand, which the Iews say was lifted up highest: or his hands, according to the other reading, which was the usual rite of blessing. See Luk. 24. 50. By this posture he signified both whence he expected the blessing, and his hearty desire of it for them.

In some such manner, as is related, Numb. 6. 24, &c. though not in the same form, as some suppose, for it is not probable that he used it before God delivered it. And this blessing was an act of his Priestly office no less than sacrificing. See Gen. 14. 18, 19. Numb. 6. 23. Deut. 10. 8. and 21. 5. Luk. 24. 50.

To wit, from the altar, whence he is said to come down, either 1. because the Altar stood upon raised ground to which they went up by an insensible ascent. Compare Exod. 20. 26. Or 2. because it was nearer the Holy place and the Holy of holies, which was the upper end.