Elementary, my dear Watson!
"Why did God cause Jericho’s walls to collapse? Only to display His divine power? Hadn’t He just parted the waters of the river Jordan for the entire nation of Israel to cross over? Here are some of Holmes’ clues: The Israelites marched around Jericho one time each of the first six days, and then seven times on the seventh day. Why? What is God trying to accomplish with all this marching? Does the number 7 have any meaning in this context? What would you have done as a soldier inside Jericho on that fateful seventh day?