Joshua 4:1-7

So it was when all the nation had finished crossing the Jordan, the LORD said to Joshua, “Take for yourselves the twelve men [chosen] from among the people, one man from each tribe, and command them, ‘Pick up for yourselves twelve stones [one each] from here out of the midst of the Jordan, from the place where the priests’ feet are standing firm; carry them over with you and lay them down at the place where you will spend the night tonight.’ ” Then Joshua called the twelve men whom he had appointed from the sons of Israel, one man from each tribe; and Joshua said to them, “Cross over again to the ark of the LORD your God into the midst of the Jordan, and each of you take up a stone on his shoulder, according to the number of the tribes of the sons of Israel, so that this may be a sign among you; when your children ask later, ‘What do these stones mean to you?’ then you shall say to them that the waters of the Jordan were cut off before the ark of the covenant of the LORD; when it crossed the Jordan, the waters of the Jordan were cut off. So these stones shall become a memorial for Israel forever.”