Numbers 8:11; Numbers 8:15; Numbers 8:24; Numbers 8:26

11 and Aaron shall offer the Levites before the LORD as a wave offering from the people of Israel, that they may do the service of the LORD.

15 And after that the Levites shall go in to serve at the tent of meeting, when you have cleansed them and offered them as a wave offering.

24 "This applies to the Levites: from twenty-five years old and upward they shall come to do duty in the service of the tent of meeting.

26 They minister to their brothers in the tent of meeting by keeping guard, but they shall do no service. Thus shall you do to the Levites in assigning their duties."