Joshua 3:1-3

Joshua got up early in the morning; then he and all the children of Israel set out from Shittim and came to the Jordan, and they spent the night there before they crossed [the river]. And it happened at the end of three days that the officers went throughout the camp, and they commanded the people, “When you see the ark of the covenant of the LORD your God being carried by the Levitical priests, then you shall set out from where you are and follow it.