Numbers 4:5-6, 15

when the camp setteth forward, Aaron shall go in, and his sons, and they shall take down the veil of the screen, and cover the ark of the testimony with it, and shall put thereon a covering of sealskin, and shall spread over it a cloth all of blue, and shall put in the staves thereof.

And when Aaron and his sons have made an end of covering the sanctuary, and all the furniture of the sanctuary, as the camp is set forward; after that, the sons of Kohath shall come to bear it: but they shall not touch the sanctuary, lest they die. These things are the burden of the sons of Kohath in the tent of meeting.