Numbers 4:3-5

BRG Bible

³ From thirty years old and upward even until fifty years old, all that enter into the host, to do the work in the tabernacle of the congregation.

⁴ This shall be the service of the sons of Kohath in the tabernacle of the congregation, about the most holy things:

⁵ ¶ And when the camp setteth forward, Aaron shall come, and his sons, and they shall take down the covering vail, and cover the ark of testimony with it: