Joshua 4:4-7, 19-24

Then Joshua called the twelve men, whom he had prepared of the children of Israel, out of every tribe a man: and Joshua said unto them, Pass over before the ark of Jehovah your God into the midst of the Jordan, and take you up every man of you a stone upon his shoulder, according unto the number of the tribes of the children of Israel; that this may be a sign among you, that, when your children ask in time to come, saying, What mean ye by these stones? then ye shall say unto them, Because the waters of the Jordan were cut off before the ark of the covenant of Jehovah; when it passed over the Jordan, the waters of the Jordan were cut off: and these stones shall be for a memorial unto the children of Israel for ever.

And the people came up out of the Jordan on the tenth day of the first month, and encamped in Gilgal, on the east border of Jericho. And those twelve stones, which they took out of the Jordan, did Joshua set up in Gilgal. And he spake unto the children of Israel, saying, When your children shall ask their fathers in time to come, saying, What mean these stones? then ye shall let your children know, saying, Israel came over this Jordan on dry land. For Jehovah your God dried up the waters of the Jordan from before you, until ye were passed over, as Jehovah your God did to the Red Sea, which he dried up from before us, until we were passed over; that all the peoples of the earth may know the hand of Jehovah, that it is mighty; that ye may fear Jehovah your God for ever.