The battle at Ai was the second in the series that Joshua took on as the Commander-in-Chief, the first being Jericho. His first attempt at Ai was a disaster – he lost 36 men. Joshua was dazed! He cried to the Lord because of the embarrassing defeat, and for the fact that it was contrary to what God had promised them – that no one would be able to stand before him. When Joshua protested the outcome of the battle, God asked him to look into the camp, for that was where the stopper could be found. Unless the stopper was removed, no other progress could be made.
It happened that there was sin in the camp. Achan had taken of the accursed thing, contrary to God’s warning. Before this, it is possible to trace another sin, though it appeared subtle. Israel committed the sin of presumption. They advised Joshua not to send all the men of war as Ai was a little place.
While you may not find many believers engage in stealing, it is different with presumption. Those who are guilty of this sin think they can handle small matters by themselves.
So they segment what they consult God about and presume to handle the rest. The result is often embarrassing disappointment. The Bible never said that we should acknowledge God with the big issues of life; rather we are enjoined to talk to Him in all our ways. As Jesus rightly said, without Him we can do nothing.