Joshua 4:9, 19-24

Then Joshua set up [a second monument of] twelve stones in the midst 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 [day] of the first month and encamped at Gilgal on the eastern border of Jericho. And those twelve stones which they had taken from the Jordan, Joshua set up in Gilgal. He said to the sons of Israel, “When your children ask their fathers in time to come, ‘What do these stones mean?’ then you shall let your children know, ‘Israel crossed this Jordan on dry ground.’ For the LORD your God dried up the waters of the Jordan for you until you crossed over, just as the LORD your God did to the Red Sea, which He dried up before us until we had crossed; so that all the peoples of the earth may know [without any doubt] and acknowledge that the hand of the LORD is mighty and extraordinarily powerful, so that you will fear the LORD your God [and obey and worship Him with profound awe and reverence] forever.”