Joshua 4:20-23

They carried with them the twelve rocks taken from the Jordan, and Joshua set them up at Gilgal. Then he spoke to the Israelites: “In the future your children will ask you, ‘What do these rocks mean?’ Tell them, ‘Israel crossed the Jordan River on dry land. The LORD your God caused the water to stop flowing until you finished crossing it, just as the LORD did to the Red Sea. He stopped the water until we crossed it.