Numbers 4:37-39

Young's Literal Translation

³⁷ These [are] those numbered of the families of the Kohathite, every one who is serving in the tent of meeting, whom Moses and Aaron numbered, by the command of Jehovah, by the hand of Moses.

³⁸ And those numbered of the sons of Gershon, by their families, and by the house of their fathers,

³⁹ 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,