Charles Ellicott Commentary Leviticus 9:15

"And he presented the people`s oblation, and took the goat of the sin-offering which was for the people, and slew it, and offered it for sin, as the first." — Leviticus 9:15 (ASV)

And he brought the people’s offering. —Being reconciled to God by the atoning sacrifice which he offered for his own share in the sin, Aaron was now qualified to offer the sin offering of the people.

As the first. —The ritual in this sacrifice Aaron conducted in the same manner as in the foregoing one offered for himself. (See Leviticus 9:8.) He accordingly burnt the flesh without the camp, for which he was reproved by Moses.