Numbers 18:5-7

King James Version

⁵ And ye shall keep the charge of the sanctuary, and the charge of the altar: that there be no wrath any more upon the children of Israel.

⁶ And I, behold, I have taken your brethren the Levites from among the children of Israel: to you they are given as a gift for the Lord, to do the service of the tabernacle of the congregation.

⁷ Therefore thou and thy sons with thee shall keep your priest's office for everything of the altar, and within the vail; and ye shall serve: I have given your priest's office unto you as a service of gift: and the stranger that cometh nigh shall be put to death.