Chapter 3: Dry Ground=River Jordan
Joshua leads the tribes of Israel to Jordan, when the feet of the priests (1 out of every 12 tribes) stepped foot into the waters of Jordan, it became dry and the Israelites were able to pass through the River Jordan on dry ground.
Chapter 4: Twelve Stones
After the last Israelite passed through the River Jordan on dry ground, the twelve men (1 from each tribe of Israel) who stepped foot into the water, in the last chapter. Is commanded to place a rock where they stood near their camp. These are the 12 stones that commemorate the crossing of Jordan.
As the Israelites crossed the river, they saw the presence of God with Joshua as he was magnified as a prophet before them. The fear and understand of the Lord, was once again seen as it was with Moses, through Joshua. Over 40,000 armed Israelites crossed the river, and as the last one crossed the river returned to its normal flow.
Joshua then tells the congregation, all of Israel to remember this day. Joshua continues, by saying that they all must remember this day and remember the 12 stones that when their children and future generations ask about the stones they can tell them that they were carried through the river Jordan on dry ground just like Moses with the power of God brought them out of bondage from the Pharaoh in Egypt as they crossed the Red Sea on dry ground. This is to be a reminder of the Lord, and his power… that we might respect, follow and fear him, as the Lord God Almighty.