Joshua 3:2-4

Three days later the Israelite officers went through the camp, giving these instructions to the people: “When you see the Levitical priests carrying the Ark of the Covenant of the LORD your God, move out from your positions and follow them. Since you have never traveled this way before, they will guide you. Stay about half a mile behind them, keeping a clear distance between you and the Ark. Make sure you don’t come any closer.”