Leviticus 9:8

Aaron therefore went unto the altar
Of burnt offering, freely and cheerfully, at the direction and introduction of Moses, who acted in this affair in the name of the Lord:

and slew the calf of the sin [offering], which [was] for himself;
which was to be offered first, as it was proper it should, that, atonement being made for his sins, his after burnt offering might be accepted with God, and he be fit to offer the sacrifices of the people: the calf he slew on the north side of the altar, where all the sin offerings and burnt offerings were slain; see ( Leviticus 1:11 ) ( 6:25 ) .