John Gill Commentary Leviticus 8:3

"and assemble thou all the congregation at the door of the tent of meeting." — Leviticus 8:3 (ASV)

And gather you all the congregation together That is, the heads of the tribes and the elders of the people, as Aben Ezra interprets it; for the whole body of the people, and every individual of them, could not be got together: unto the door of the tabernacle of the congregation ; taking this for the whole court itself, as it sometimes is; though no doubt on this occasion as great a number was convened as well could be admitted into the court, or about it, to be spectators and witnesses of the solemn investiture of Aaron and his sons with the priestly office.