Joshua 3:2

Joshua got up early in the morning; and they moved from Shittim and came to the Jordan, he and all the children of Israel. They camped there before they crossed over.

and they commanded the people, saying, “When you see the ark of the LORD your God’s covenant, and the Levitical priests bearing it, then leave your place and follow it.

Yet there shall be a space between you and it of about two thousand cubits by measure—don’t come closer to it—that you may know the way by which you must go; for you have not passed this way before.”

Joshua said to the people, “Sanctify yourselves; for tomorrow the LORD will do wonders among you.”