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.
We have here a second muster of the tribe of Levi. As that tribe was taken out of all Israel to be God's peculiar, so the middle-aged men of that tribe were taken from among the rest to be actually employed in the service of the tabernacle. Now observe, I. Who were to be taken into this number. All the males from thirty years old to fifty.
Commenting on Numbers 4:1-20
And when the camp setteth forward,.... Upon the cloud's removing and the trumpets blowing: Aaron shall come, and his sons; into the holy place: and they shall take down the covering vail: the vail that divided between the holy and the most holy place, which covered all in the holy of holies out of sight: and cover the ark of testimony with it; together with...
covering veil--the inner veil, which separated the holy from the most holy place. (See on Exo 36:35).