"So Joshua called together the twelve men he had appointed from the Israelites, one from each tribe, and said to them, 'Go over before the ark of the Lord your God into the middle of the Jordan. Each of you is to take up a stone on his shoulder, according to the number of the tribes of the Israelites, to serve as a sign among you. In the future, when your children ask you, "What do these stones mean?" tell them that the flow of the Jordan was cut off before the ark of the covenant of the Lord. When it crossed the Jordan, the waters of the Jordan were cut off. These stones are to be a memorial to the people of Israel forever.'" NIV translation
In chapter 3, we looked at walking in the power of God. Here we see the fact that God wants us to remember that He is the source of all power. The danger for us, as mere men, is that we can get so caught up in the power that we have that it can go to our heads. This can open the door to pride which separates us from God just as it did with Satan. We also see that we have to tell others that it is God at work and not ourselves. This is especially true for our children and grandchildren as we see that these stones were to be a reminder for the children of those who crossed the Jordan. This testimony is how we overcome the schemes of the devil as we see in Revelation 12. There is power in remembering and sharing what God has done and that is why the devil tries to keep us quiet.