Joshua 4:8-9

So the [twelve men chosen from the] sons of Israel did as Joshua commanded, and took up twelve stones out of the midst of the Jordan, according to the number of the tribes of the sons of Israel, just as the LORD had spoken to Joshua; and they carried them over with them to the place where they were spending the night and put them down there. 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.