Numbers 3:5 - 3:10
5 Then Yahweh spoke to Moses, saying, 6 “Bring the tribe of Levi near and have them stand before Aaron the priest, that they may minister to him. 7 And they shall keep his responsibility and the responsibility for the whole congregation before the tent of meeting, to perform the service of the tabernacle. 8 They shall also keep all the furnishings of the tent of meeting, along with the responsibility of the sons of Israel, to perform the service of the tabernacle. 9 You shall thus give the Levites to Aaron and to his sons; they are wholly given to him from among the sons of Israel. 10 So you shall appoint Aaron and his sons that they may keep their priesthood, but the outsider who comes near shall be put to death.”