6 that this may be a sign among you, that when your children ask in time to come, saying, ‘What do you mean by these stones?’ 7 then you shall tell them, ‘Because the waters of the Jordan were cut off before the ark of the covenant of Yahweh. When it passed over the Jordan, the waters of the Jordan were cut off. These stones shall be for a memorial to the children of Israel forever.’” 8 The children of Israel did as Joshua commanded, and took up twelve stones out of the middle of the Jordan, as Yahweh spoke to Joshua, according to the number of the tribes of the children of Israel; and they carried them over with them to the place where they lodged, and laid them down there.
Matthew Henry's Commentary on Joshua 4:6-8
Commentary on Joshua 4:1-9
(Read Joshua 4:1-9)
The works of the Lord are so worthy of rememberance, and the heart of man is so prone to forget them, that various methods are needful to refresh our memories, for the glory of God, our advantage, and that of our children. God gave orders for preparing this memorial.