Aaron therefore went unto the altar, and slew the calf of the sin offering, which was for himself.

Jamieson-Fausset-Brown Bible Commentary

8. Aaron . went unto the altar, and slew the calf of the sin offering-Whether it had been enjoined the first time, or was unavoidable from the divisions of the priestly labor not being as yet completely arranged, Aaron, assisted by his sons, appears to have slain the victims with his own hands, as well as gone through all the prescribed ritual at the altar.

Matthew Henry's Concise Commentary

9:1-21 These many sacrifices, which were all done away by the death of Christ, teach us that our best services need washing in his blood, and that the guilt of our best sacrifices needs to be done away by one more pure and more noble than they. Let us be thankful that we have such a High Priest. The priests had not a day's respite from service allowed. God's spiritual priests have constant work, which the duty of every day requires; they that would give up their account with joy, must redeem time. The glory of God appeared in the sight of the people, and owned what they had done. We are not now to expect such appearances, but God draws nigh to those who draw nigh to him, and the offerings of faith are acceptable to him; though the sacrifices being spiritual, the tokens of the acceptance are spiritual likewise. When Aaron had done all that was to be done about the sacrifices, he lifted up his hands towards the people, and blessed them. Aaron could but crave a blessing, God alone can command it.