Exodus 28:1

Aaron and his sons Hitherto every master of a family was priest to his own family. But now, as the families of Israel began to be incorporated into a nation, and a tabernacle of the congregation was to be erected, as a visible centre of their unity, it was requisite there should be a public priesthood instituted. Moses, who had hitherto officiated, and is therefore reckoned among the priests of the Lord, (Psalms 99:6,) had enough to do as their prophet, to consult the oracle for them, and as their prince, to judge among them. Nor was he desirous to engross all the honours to himself, or to entail that of the priesthood, which alone was hereditary, upon his own family; but was very well pleased to see his brother Aaron invested with this office, and his sons after him; while (how great soever he himself was) his sons after him would be but common Levites. It is an instance of the humility of that great man, and an evidence of his sincere regard to the glory of God, that he had so little regard to the preferment of his own family. Aaron, that had humbly served as a prophet to his younger brother Moses, and did not decline the office, is now advanced to be a priest to God. God had said to Israel in general, that they should be to him a kingdom of priests; but because it was requisite that those who ministered at the altar should give themselves wholly to the service of God, he had chosen from among them one to be a family of priests, the father and his four sons; and from Aaron's loins descended all the priests of the Jewish Church, whom we read of both in the Old Testament and in the New.