Joshua 4:5

3and command them, saying, ‘Take from out of the middle of the Jordan, out of the place where the priests’ feet stood firm, twelve stones, carry them over with you, and lay them down in the place where you’ll camp tonight.’”

4Then Joshua called the twelve men whom he had prepared of the children of Israel, a man out of every tribe.

5Joshua said to them, “Cross before the ark of the LORD your God into the middle of the Jordan, and each of you pick up a stone and put it on your shoulder, according to the number of the tribes of the children of Israel;

6that this may be a sign among you, that when your children ask in the future, saying, ‘What do you mean by these stones?’

7then you shall tell them, ‘Because the waters of the Jordan were cut off before the ark of the LORD’s covenant. When it crossed over the Jordan, the waters of the Jordan were cut off. These stones shall be for a memorial to the children of Israel forever.’”