And gather thou all the congregation together unto the door of the tabernacle of the congregation.
All the congregation — The elders who represented all, and as many of the people as would, and could get thither, that all might be witnesses both of Aaron's commission from God, and of his work and business.
 And he poured of the anointing oil upon Aaron's head, and anointed him, to sanctify him.
He poured — In a plentiful manner, as appears from Psalms 133:2, whereas other persons and things were only sprinkled with it: because his unction was to typify the anointing of Christ with the Spirit, which was not given by measure to him. A measure of the same anointing is given to all believers.
 And he brought the bullock for the sin offering: and Aaron and his sons laid their hands upon the head of the bullock for the sin offering.
The bullock — There were indeed seven bullocks to be offered at his consecration, one every day; but here he mentions only one, because he here describes only the work of the first day.
 But the bullock, and his hide, his flesh, and his dung, he burnt with fire without the camp; as the LORD commanded Moses.
His hide — Which in the offerings for the people was not burnt, but given to the priest.
 And he brought the ram for the burnt offering: and Aaron and his sons laid their hands upon the head of the ram.
He brought the ram — Hereby they gave to God the glory of this great honour which was put upon them: and also signified the devoting themselves and all their service to God.
 And he killed it; and Moses sprinkled the blood upon the altar round about.
He — Either Moses, as in the following clause, or some other person by his appointment; which may be the reason why he is not named here, as he is to the sprinkling of the blood, which was an action more proper to the priest, and more essential to the sacrifice.
 And Moses took the breast, and waved it for a wave offering before the LORD: for of the ram of consecration it was Moses' part; as the LORD commanded Moses.
Moses's part — Who at this time administering the priest's office was to receive the priest's wages.
 And Moses said unto Aaron and to his sons, Boil the flesh at the door of the tabernacle of the congregation: and there eat it with the bread that is in the basket of consecrations, as I commanded, saying, Aaron and his sons shall eat it.
The flesh — That which was left of the ram, and particularly the breast, which was said to be Moses's part, Leviticus 8:29, and by him was given to Aaron, that he and his sons might eat of it, in token that they and only they should have the right to do so for the future.
 And ye shall not go out of the door of the tabernacle of the congregation in seven days, until the days of your consecration be at an end: for seven days shall he consecrate you.
Seven days — In each of which the same ceremonies were to be repeated, and other rites to be performed.
He — Either God or Moses; for the words may be spoken by Moses, either in God's name or in his own; Moses speaking of himself in the third person, which is very common in scripture.
 So Aaron and his sons did all things which the LORD commanded by the hand of Moses.
So Aaron and his sons did all things — And thus the covenant of life and peace, Hebrews 7:21. For neither these priests, nor their priesthood was to continue. But His is a perpetual and unchangeable priesthood.