Numbers 4:5-6, 15

“When the camp prepares to move out, Aaron and his sons shall come into the sanctuary and take down the veil (curtain) screening off the Holy of Holies, and cover the ark of the testimony with it; and they shall put on it a covering of porpoise skin (fine leather), and shall spread over that a cloth of pure blue, and shall insert the carrying poles of the ark.

When Aaron and his sons have finished covering the sanctuary and all its furniture, as the camp sets out, after all that [is done, but not before], the sons of Kohath shall come to carry them [using the poles], so that they do not touch the holy things, and die. These are the things in the Tent of Meeting (tabernacle) which the sons of Kohath are to carry.