4.7 Joshua -- Achan
Israel next attacked Ai, a small town west of Jericho. Joshua sent only a few thousand soldiers against a small group of defenders. Surprisingly, they were defeated by the men of Ai. Joshua and the elders of Israel prostrated themselves before the Lord. The Lord told him that some Israelites had stolen some of the devoted things from Jericho. Actually, it was only one man, but God attributed the sin to all Israel. "One soldier's theft of the devoted goods brought collective guilt on the entire nation" (NIV, p 300, footnote). His action led to not just the defeat of Israel in battle, but even more seriously, the departure of the Lord's Presence!
"I will not be with you anymore unless you destroy whatever among you is devoted to destruction" (Josh 7:12).
There's one in every crowd -- a guy who volunteers to be the next to undergo a painful death: we had Korah, the man who picked up sticks on the Sabbath, the man who took a Midianite woman into his tent in the sight of Moses, and now Achan. They have not yet learned: little things matter a lot to the God of Israel. 90% obedience is still counted as disobedience. "Doing better next time" is not an option. One strike and you're out. Note also that the same law of guilt by affiliation that was applied to the inhabitants of Jericho also applied to Israel -- all Achan's children and animals were put to death for the sin of the father (Josh 7:24-25).
After the execution of Achan, the attack on Ai resumed. It was carried out with thoroughness and ruthlessness, to the tune of 12,000 dead Canaanites.