Joshua 3:6

And Joshua spake unto the priests, saying, Take up the Ark of the Covenant and pass over before the people. This was the special work of the sons of Kohath, Numbers 4:15, and the order referred to the actual time of marching. and they took up the Ark of the Covenant and went before the people, this statement either anticipating the actual event, or having reference to the fact that the priests took up their station at the head of the army, ready for the march of the next day.