Joshua 4:3; Joshua 4:8

3 and tell them to take up twelve stones from the middle of the Jordan, from right where the priests are standing, and carry them over with you and put them down at the place where you stay tonight.”

8 So the Israelites did as Joshua commanded them. They took twelve stones from the middle of the Jordan, according to the number of the tribes of the Israelites, as the LORD had told Joshua; and they carried them over with them to their camp, where they put them down.