6 that this may be a sign among you, that, when your children ask in time to come, saying, What mean ye by these stones? 7 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. 8 And the children of Israel did so as Joshua commanded, and took up twelve stones out of the midst of the Jordan, as Jehovah spake unto Joshua, according to the number of the tribes of the children of Israel; and they carried them over with them unto 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.