Joshua 3:3-4 NIV

[3] giving orders to the people: “When you see the ark of the covenant of the LORD your God, and the Levitical priests carrying it, you are to move out from your positions and follow it. [4] Then you will know which way to go, since you have never been this way before. But keep a distance of about two thousand cubits between you and the ark; do not go near it.”