Numbers 8:15
After you have cleansed them and presented them as a wave offering, they may come to serve at the Tent of Meeting.
Berean Standard Bible
And after that shall the Levites go in to do the service of the tabernacle of the congregation: and thou shalt cleanse them, and offer them for an offering.
“After that, the Levites shall go in to do the service of the Tent of Meeting. You shall cleanse them, and offer them as a wave offering.