Joshua 4:8-9

8The Israelites did just as Joshua commanded. They picked up twelve stones, according to the number of the Israelite tribes, from the middle of the Jordan as the Lord had instructed Joshua. They carried them over with them to the camp and put them there.

9Joshua also set up twelve stonesin the middle of the Jordan in the very place where the priests carrying the ark of the covenant stood. They remain there to this very day.