Joshua 3:3-5

and they commanded the people, saying, “When you see the ark of the covenant of the LORD your God, and the priests, the Levites, bearing it, then you shall set out from your place and go after it. Yet there shall be a space between you and it, about two thousand cubits by measure. Do not come near it, that you may know the way by which you must go, for you have not passed this way before.” And Joshua said to the people, “Sanctify yourselves, for tomorrow the LORD will do wonders among you.”