Numbers 8:8-11, 20-22

“Have them take a young bull with its accompanying Grain-Offering of fine flour mixed with oil, plus a second young bull for an Absolution-Offering. Bring the Levites to the front of the Tent of Meeting and gather the entire community of Israel. Present the Levites before GOD as the People of Israel lay their hands on them. Aaron will present the Levites before GOD as a Wave-Offering from the People of Israel so that they will be ready to do GOD’s work.

Moses, Aaron, and the entire community of the People of Israel carried out these procedures with the Levites, just as GOD had commanded Moses. The Levites purified themselves and scrubbed their clothes. Then Aaron presented them as a Wave-Offering before GOD and made atonement for them to purify them. Only then did the Levites go to work at the Tent of Meeting. Aaron and his sons supervised them following the directions GOD had given.