Numbers 4:3-5

21st Century King James Version

³ from thirty years old and upward even until fifty years old, all who 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 concerned with the most holy things.

⁵ And when the camp moves forward, Aaron shall come and his sons, and they shall take down the covering veil and cover the ark of Testimony with it,