Numbers 3:8-10

Revised Standard Version

⁸ they shall have charge of all the furnishings of the tent of meeting, and attend to the duties for the people of Israel as they minister at the tabernacle. ⁹ And you shall give the Levites to Aaron and his sons; they are wholly given to him from among the people of Israel. ¹⁰ And you shall appoint Aaron and his sons, and they shall attend to their priesthood; but if any one else comes near, he shall be put to death.”