Joshua 3:3-5

3:3 and commanded the people: “When you see the ark of the covenant of the Lord your God being carried by the Levitical priests, you must leave here and walk behind it. 3:4 But stay about three thousand feet behind it. Keep your distance so you can see which way you should go, for you have not traveled this way before.”

3:5 Joshua told the people, “Ritually consecrate yourselves, for tomorrow the Lord will perform miraculous deeds among you.”