Jamieson, Fausset and Brown on Leviticus 8:7-9

7-9. he put upon him the coat, and girded him with the girdle--The splendor of the official vestments, together with the gorgeous tiara of the high priest, was intended, doubtless, in the first instance, to produce in the minds of the people a high respect for the ministers of religion; and in the next, from the predominant use of linen, to inculcate upon Aaron and his sons the duty of maintaining unspotted righteousness in their characters and lives.