"What do these stones mean to you?"

So 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 again to the ark of the LORD your God into the middle 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.
"Let this be a sign among you, so that when your children ask later, saying,
'What do these stones mean to you?' then you shall say to them,
'Because the waters of the Jordan were cut off before the ark of the covenant of the LORD;
when it crossed the Jordan, the water of the Jordan were cut off.'
So these stones shall become a memorial to the sons of Israel forever."

... And it came about when the priests who carried the ark of the covenant of the LORD had come up from the middle of the Jordan, and the soles of the priests' feet were lifted up to the dry ground, that the waters of the Jordan returned to their place, and went over all its banks as before.

Now the people came up from the Jordan on the tenth of the first month
and camped at Gilgal on the eastern edge of Jericho.
And those twelve stones which they had taken from the Jordan,
Joshua set up at Gilgal.
And he said to the sons of Israel,
"When your children ask their fathers in time to to come,
saying 'What are these stones?' then you shall inform your children, saying,
'Israel crossed this Jordan on dry ground.'
For the LORD your God dried up the waters of the Jordan before you until you had crossed,
just as the LORD your God had done to the Red Sea,
which He dried up before us until we had crossed;
that all the peoples of the earth may know that the hand of the LORD is mighty,
so that you may fear the LORD your God forever."
Joshua 4: 4-7, 18-24