Numbers 8:11

8:11 and Aaron is to offer the Levites before the Lord as a wave offering from the Israelites, that they may do the work of the Lord.

Numbers 8:13

8:13 You are to have the Levites stand before Aaron and his sons, and then offer them as a wave offering to the Lord.

Numbers 3:12

3:12 “Look, I myself have taken the Levites from among the Israelites instead of every firstborn who opens the womb among the Israelites. So the Levites belong to me,