Joshua 4:5-9

And Joshua said to them, “Pass on before the ark of the LORD your God into the midst of the Jordan, and take up each of you a stone upon his shoulder, according to the number of the tribes of the people of Israel, that this may be a sign among you. When your children ask in time to come, ‘What do those stones mean to you?’ then you shall tell them that the waters of the Jordan were cut off before the ark of the covenant of the LORD. When it passed over the Jordan, the waters of the Jordan were cut off. So these stones shall be to the people of Israel a memorial forever.” And the people of Israel did just as Joshua commanded and took up twelve stones out of the midst of the Jordan, according to the number of the tribes of the people of Israel, just as the LORD told Joshua. And they carried them over with them to the place where they lodged and laid them down there. And Joshua set up twelve stones in the midst of the Jordan, in the place where the feet of the priests bearing the ark of the covenant had stood; and they are there to this day.