Numbers 4:3-5

Revised Standard Version

³ from thirty years old up to fifty years old, all who can enter the service, to do the work in the tent of meeting. ⁴ This is the service of the sons of Kohath in the tent of meeting: the most holy things. ⁵ When the camp is to set out, Aaron and his sons shall go in and take down the veil of the screen, and cover the ark of the testimony with it;