And the Levites purified themselves and washed their clothes; then Aaron presented them like a wave offering before the LORD, and Aaron made atonement for them to cleanse them.
Numbers 8:21
Surrounding context
8:20 Thus Moses and Aaron and all the congregation of the children of Israel did to the Levites; according to all that the LORD commanded Moses concerning the Levites, so the children of Israel did to them.
8:21 And the Levites purified themselves and washed their clothes; then Aaron presented them like a wave offering before the LORD, and Aaron made atonement for them to cleanse them.
8:22 After that the Levites went in to do their work in the tabernacle of meeting before Aaron and his sons; as the LORD commanded Moses concerning the Levites, so they did to them.