Leviticus 9:12

‘And he slew the whole burnt offering, and Aaron's sons delivered to him the blood, and he sprinkled it on the altar round about.’

Then similar procedures were observed for the whole burnt offering. It was for his atonement and dedication, as well as that of the people. Aaron slew it, his sons caught the blood, and Aaron sprinkled it on all four sides of the altar. Atonement was made and he was thereby dedicated to God.