Joshua 4:4-9

So Joshua summoned the twelve men he had selected from the Israelites, one per tribe. Joshua instructed them, “Walk out to the middle of the riverbed to the ark of YAHWEH your God. Each of you choose a stone and lift it up onto your shoulder—one stone for each tribe. The stones will always be a sign to you. Someday, when your children ask you, ‘Why are these stones so important?’ tell them, ‘The Jordan stopped flowing in front of the ark of the covenant of YAHWEH—the floodwaters were completely cut off.’ These stones will serve as a memorial for Israel forever.” The Israelites did as Joshua commanded them. They took twelve stones according to the number of the tribes of Israel, from the middle of the riverbed, and carried them to the camp and put them there. Joshua set up the memorial stones that they had taken from the exact spot where the priests stood bearing the ark in the riverbed. They remain there to this day.