Joshua 4:9, 19-24

Then Joshua set up twelve stones in the middle of the Jordan at the place where the feet of the priests who carried the ark of the covenant were standing, and they are there to this day.

Now the people came up from the Jordan on the tenth of the first month and camped at Gilgal on the eastern edge of Jericho. Those twelve stones which they had taken from the Jordan, Joshua set up at Gilgal. He said to the sons of Israel, “When your children ask their fathers in time to come, saying, ‘What are these stones?’ then you shall inform your children, saying, ‘Israel crossed this Jordan on dry ground.’ For the LORD your God dried up the waters of the Jordan before you until you had crossed, just as the LORD your God had done to the Red Sea, which He dried up before us until we had crossed; that all the peoples of the earth may know that the hand of the LORD is mighty, so that you may fear the LORD your God forever.”