6 So that this may be a sign among you; when your children say to you in time to come, What is the reason for these stones? 7 Then you will say to them, Because the waters of Jordan were cut off before the ark of the Lord's agreement; when it went over Jordan the waters of Jordan were cut off: and these stones will be a sign for the children of Israel, keeping it in their memory for ever. 8 So the children of Israel did as Joshua gave them orders, and took twelve stones from the middle of Jordan, as the Lord had said to Joshua, one for every tribe of the children of Israel; these they took across with them to their night's resting-place and put 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.