Then they shall remove the ashes from the bronze altar, spread a purple cloth over 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 they shall take away the ashes from the altar, and spread a purple cloth thereon. Having cleared the holy of holies, and the holy place, they were to come forth from thence into the court of the tabernacle, where stood the altar of burnt offering, which is here meant, and on which sacrifices being daily burnt, there were always ashes to be removed; and...
shall take away the ashes from the altar, &c.--The necessity of removing ashes from the altar plainly implies that sacrifices were offered in the wilderness (compare Exo 18:12; Exo 24:4), though that rebellious race seems frequently to have neglected the duty (Amo 5:25).