Joshua 3:3

3. When ye see the ark of the covenant This was a chest made of shittim or acacia wood, four feet in length, and two and one third feet in breadth and depth. It was overlaid with gold within and without. The cover, which was edged with gold, was called the mercy-seat. Standing on this lid were the cherubim with outstretched wings. The ark was borne upon the shoulders by means of rods passing through two rings on each of the two sides. When transported, it was enveloped in the veil of the dismantled tabernacle, the curtain of badger skins, and the blue cloth, (Numbers 4:5-6,) and was therefore not seen. Its name is derived from its chief contents, the “covenant of Sinai” the two tables of stone, on which was the Decalogue, written by the finger of God. From Hebrews 9:4, we learn that it contained also “the pot of manna,” and “Aaron’s rod that budded.” It was never seen save by the high priest, thus symbolizing the invisible Jehovah. See on Exodus 25:10-22.

And the priests the Levites The Levite-priests, as distinguished from all irregular priests who are not Levitical. Such occasionally arose in times of apostasy from the law. On ordinary occasions the Levites of the house of Kohath, by special command, bore the ark. But when removed from within the veil, or when borne on festive occasions of extraordinary interest, the priests, the offspring of Aaron, were the bearers. Joshua 6:6 and 1 Kings 8:3; 1 Kings 8:6.

Go after it Let the ark of God be your leader, and move ye as the ark moves. Heretofore it stood at the centre when Israel was encamped, and in mid army when they marched. The ark now led them, as heretofore the pillar of fire.