When they went into the tent of the congregation
Not only at this time, but at all other times:
and when they came near unto the altar, they washed;
to the altar of burnt offering to offer sacrifice; and also to the altar of incense, and burn incense on that; for before whatever service they performed in the tabernacle they washed:
as the Lord commanded Moses;
( Exodus 30:20 ) this phrase is near twenty times expressed in this and the preceding chapter, to show that everything was done by the workmen, and everything put in its proper place by Moses, exactly according to the will of God; no one pursuing his own fancy and private judgment, but all consulting the mind of God, and acting according to that.