Joshua 3:2-4

At the end of three days the officers went through the midst of the camp; and they commanded the people, saying, “When you see the ark of the covenant of the LORD your God with the Levitical priests carrying it, then you shall set out from your place and go after it. However, there shall be between you and it a distance of about 2,000 cubits by measure. Do not come near it, that you may know the way by which you shall go, for you have not passed this way before.”