Numbers 8:9

You shall do this to them, to cleanse them: sprinkle the water of cleansing on them, let them shave their whole bodies with a razor, and let them wash their clothes, and cleanse themselves.

Then let them take a young bull, and its meal offering, fine flour mixed with oil; and another young bull you shall take for a sin offering.

You shall present the Levites before Yahweh. The children of Israel shall lay their hands on the Levites,

and Aaron shall offer the Levites before Yahweh for a wave offering, on the behalf of the children of Israel, that it may be theirs to do the service of Yahweh.