Joshua 4:7

7.Then you shall answer them, etc Although the stones themselves cannot speak, yet the monument furnished the parents with materials for speaking, and for making the kindness of God known to their children. And here zealous endeavors to propagate piety are required of the aged, (50) and they are enjoined to exert themselves in instructing their children. For it was the will of God that this doctrine should be handed down through every age; that those who were not then born being afterwards instructed by their parents might become witnesses to it from hearing, though they had not seen it with their eyes.

The stones were placed according to the number of the tribes, that each might be incited to gratitude by its own symbol. It is true that two tribes and a half tribe who had obtained their inheritance beyond the Jordan, had not, when considered apart from the others, any occasion for making that passage. But as the land of Canaan was possessed by the others for the common good of the whole race of Abraham, so it behooved those who were all engaged in the same or a common cause not to be separated from each other. And although as yet mention had been made only of twelve men, it is obvious from a short clause, that the divine command had been declared to the whole people; for it is said that the children of Israel obeyed the words of Joshua. Nay, it is even probable that deputies were elected by suffrage to carry the stones in the name of the whole people.