Numbers 4:5-6, 15

“When the camp sets out, Aaron and his sons shall go in and they shall take down the veil of the screen and cover the ark of the testimony with it; and they shall lay a covering of porpoise skin on it, and shall spread over it a cloth of pure blue, and shall insert its poles.

When Aaron and his sons have finished covering the holy objects and all the furnishings of the sanctuary, when the camp is to set out, after that the sons of Kohath shall come to carry them, so that they will not touch the holy objects and die. These are the things in the tent of meeting which the sons of Kohath are to carry.