Numbers 4:33-35

Young's Literal Translation

³³ `This [is] the service of the families of the sons of Merari, for all their service, in the tent of meeting, by the hand of Ithamar son of Aaron the priest.'

³⁴ And Moses numbereth -- Aaron also, and the princes of the company -- the sons of the Kohathite, by their families, and by the house of their fathers,

³⁵ from a son of thirty years and upward even unto a son of fifty years, every one who is going in to the host, for service in the tent of meeting,