They commanded the people, in Joshua's name, and by his authority. The priests the Levites, who were not only Levites, but priests also. For although the Levites were to carry the ark, Num 4, yet the priests might perform that office, and did so upon some solemn occasions, as here, and Joshua 6:6. Go after it towards Jordan, to go over it in such manner as I am about to describe. Till this time the ark went in the middle of the cloudy pillar, probably being now vanished, now it goes in the front.
Related Commentaries of Joshua 3:3
Joshua 3:3
3 And they commanded the people, saying, When ye see the ark of the covenant of the LORD your God, and the priests the Levites bearing it, then ye shall remove from your place, and go after it.