Joshua 4:1-9

1 After the whole nation had finished crossing the Yarden, ADONAI said to Y'hoshua,
2 "Take for yourselves from the people twelve men, a man from every tribe;
3 and give them this order: 'Take twelve stones from the middle of the Yarden riverbed, where the cohanim are standing, carry them over with you and set them down in the place where you will camp tonight.'"
4 Y'hoshua called the twelve men whom he had chosen from the people of Isra'el, a man from every tribe,
5 and said to them, "Go on ahead of the ark of ADONAI your God into the riverbed of the Yarden. Then, each of you take a stone on his shoulder, corresponding to the number of tribes of the people of Isra'el.
6 This will be a sign for you. In the future, when your children ask, 'What do you mean by these stones?'
7 you will answer them, 'It's because the water in the Yarden was cut off before the ark for the covenant of ADONAI; when it crossed the Yarden, the water in the Yarden was cut off; and these stones are to be a reminder for the people of Isra'el forever.'"
8 The people of Isra'el did just as Y'hoshua had ordered. They took twelve stones out of the Yarden riverbed, as ADONAI had said to Y'hoshua, corresponding to the number of the tribes of the people of Isra'el, carried them over with them to the place where they were camping, and set them down there.
9 Y'hoshua also set up twelve stones in the Yarden River itself, in the place where the feet of the cohanim carrying the ark for the covenant had stood. They are there to this day.