A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
lev 8:2MOSES CONSECRATES AARON AND HIS SONS. (Lev. 8:1-36)
Take Aaron and his sons--The consecration of Aaron and his sons had been ordered long before (Exo. 29:1-46), but it is now described with all the details of the ceremonial, as it was gone through after the tabernacle was completed and the regulations for the various sacrifices enacted.
lev 8:3gather thou all the congregation together, &c.--It was manifestly expedient for the Israelitish people to be satisfied that Aaron's appointment to the high dignity of the priesthood was not a personal intrusion, nor a family arrangement between him and Moses; and nothing, therefore, could be a more prudent or necessary measure, for impressing a profound conviction of the divine origin and authority of the priestly institution, than to summon a general assembly of the people, and in their presence perform the solemn ceremonies of inauguration, which had been prescribed by divine authority.
lev 8:6Moses . . . washed them with water--At consecration they were subjected to entire ablution, though on ordinary occasions they were required, before entering on their duties, only to wash their hands and feet. This symbolical ablution was designed to teach them the necessity of inward purity, and the imperative obligation on those who bore the vessels and conducted the services of the sanctuary to be holy.
lev 8:7he 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.
lev 8:10took the anointing oil, &c.--which was designed to intimate that persons who acted as leaders in the solemn services of worship should have the unction of the Holy One both in His gifts and graces.
lev 8:14brought the bullock for the sin offering, &c.--a timely expression of their sense of unworthiness--a public and solemn confession of their personal sins and a transference of their guilt to the typical victim.
lev 8:18brought the ram, &c.--as a token of their entire dedication to the service of God.
lev 8:22brought the other ram,--&c. After the sin offering and burnt offering had been presented on their behalf, this was their peace offering, by which they declared the pleasure which they felt in entering upon the service of God and being brought into close communion with Him as the ministers of His sanctuary, together with their confident reliance on His grace to help them in all their sacred duties.
lev 8:33ye shall not go out of the door of the tabernacle of the congregation, &c.--After all these preliminaries, they had still to undergo a week's probation in the court of the tabernacle before they obtained permission to enter into the interior of the sacred building. During the whole of that period the same sacrificial rites were observed as on the first day, and they were expressly admonished that the smallest breach of any of the appointed observances would lead to the certain forfeiture of their lives [Lev 8:35].