Numbers 8:21-23

Young's Literal Translation

²¹ And the Levites cleanse themselves, and wash their garments, and Aaron waveth them a wave-offering before Jehovah, and Aaron maketh atonement for them to cleanse them,

²² and afterwards have the Levites gone in to do their service in the tent of meeting, before Aaron and before his sons; as Jehovah hath commanded Moses concerning the Levites, so they have done to them.

²³ And Jehovah speaketh unto Moses, saying,