Throughout scripture we see numerous examples of God's power at work. Many times, such as in the story of Joshua and Achan, God acts in a manner that removes any doubt of His sovereignty. It would serve us well to take these into account and look inwardly to see if we trust fully in God’s faithfulness or if at the first sign of things looking different than expected, we crumble.
The events that follow the fall of Jericho also teach us that we must earnestly pray and examine ourselves to find what may exist within us that needs to be exposed and removed. When we do not reflect and confess our sin, we are in danger of continuing in a pattern that will likely harden our hearts and cause us to be numb to our own destruction. It’s important when we confess that we are specific to what we have done and reflect with deep regret. One thing Achan did correctly was that he confessed his sin in detail. Unfortunately, he chose not to do so until his hand was forced, resulting in the consequences foretold.
For further study read Joshua 6 and 7.