Numbers 4:45-47

Young's Literal Translation

⁴⁵ These [are] those numbered of the families of the sons of Merari, whom Moses and Aaron numbered, by the command of Jehovah, by the hand of Moses.

⁴⁶ All those numbered, whom Moses numbered -- Aaron also, and the princes of Israel -- of the Levites, by their families, and by the house of their fathers,

⁴⁷ from a son of thirty years and upward even unto a son of fifty years, every one who is going in to do the work of the service, even the service of burden in the tent of meeting,