One man's sin! There were no accomplices. Nobody even saw him do it, yet Israel's army became paralyzed with fear. Joshua faltered and became confused. The whole nation was affected. Thirty-six men died. Thirty-six women became widows. And how many children no longer had a father?
One might say that the sin was somewhat atoned for. When they found out what Achan had done, Achan and his family (who were innocent of the deed) were put to death. When God saw it, however, He analyzed the sin according to different standards. He was dealing with His people, and He wanted to make sure that a witness was made—so that there would be information for those of His church in the end time.
God takes a personal interest in His people. Things happen out in the world, and He seems to do nothing. But when things happen within His church, He is concerned for the well-being of His people, and He takes action.
What we see here is a clear beginning of "the body" analogy that later becomes so important to the church in the New Testament. He shows us plainly that sin has a natural leavening effect. It increases; it will not just lie there and die. Corrections must be made to ensure that it does not spread, affecting others.
John W. Ritenbaugh
Every Action Has a Reaction