Numbers 4:5

Whenever the camp sets out, Aaron and his sons are to go in, take down the veil of the curtain, and cover the ark of the Testimony with it.

Note That is, the ark of the covenant

BSB · Berean Standard Bible
And when the camp setteth forward, Aaron shall come, and his sons, and they shall take down the covering vail, and cover the ark of testimony with it:
KJV · King James Version
When the camp moves forward, Aaron shall go in with his sons; and they shall take down the veil of the screen, cover the ark of the Testimony with it,
WEB · World English Bible
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,
ASV · American Standard Version

Related passages

From the Treasury of Scripture Knowledge, grouped by the word they explain.

And when
Numbers 2:16, 17; Numbers 10:14
Aaron shall come
The law prohibiting any person, except the high priest on one day in the year, to enter into the most holy place, must have admitted an exception while the Israelites were in the wilderness: that exception, therefore, is here expressly made; and the directions given respecting it must be religiously observed, or the service could not be safely performed. While the cloud rested on the tabernacle, the general rule was in force; but when it was removed, then the priests might enter to prepare the sacred vessels for removal.
Numbers 4:15; Numbers 3:27–32
they shall
Exodus 26:31–33; Exodus 36:35; Exodus 40:3; Isaiah 25:7; Matthew 27:51; Hebrews 9:3; Hebrews 10:20
and cover
Exodus 25:10–22; Exodus 37:1–9; 2 Samuel 6:2–9