Numbers 8:7

7.And thus shalt thou do unto them. Aaron is commanded first to sprinkle the water of purifying upon them, to cleanse them from their uncleanness; and not only so, but they are commanded to wash their clothes, that they may diligently beware of any impurity being anywhere about them, whereby their persons may be infected. Thirdly, they are commanded to shave their skin with a razor, that, putting off their flesh, they may begin to be new men. A sacrifice is afterwards added, and that twofold, to make an atonement for them. These things being completed, Aaron, in right and to the honor of the priesthood, is commanded to offer them just like the holy bread or incense. But the end of this was, that they might acknowledge that they were no longer their own masters, but devoted to God, that they might engage themselves in the service of the sanctuary. It was in testimony of alienation that some of the people were ordered at the same time to lay their hands upon them; as if by this ceremony all the tribes bore witness that with their consent the Levites passed over to be God’s peculiar property, that they might be a part or appendage of the sanctuary. For private individuals (as we shall see hereafter) were accustomed to lay their hands on their sacrifices, yet not with the same object as the priests. (177)