Joshua 4:8-9

8And the children of Israel did so, as Joshua had commanded, and took up twelve stones out of the midst of the Jordan, as Jehovah had spoken to Joshua, according to the number of the tribes of the children of Israel; and they carried them over with them to the lodging-place, and laid them down there.

9And twelve stones did Joshua set up in the midst of the Jordan, in the place where the feet of the priests who bore the ark of the covenant had stood firm; and they are there to this day.