Yet, one man, Achan, failed in his obedience to the Lord's instructions. It was a secret sin--apparently no one knew about it, not even his family. One man's disobedience to God's instructions caused the Lord to remove his hand of victory from his people when they went to battle against the city of Ai. It is interesting to note that when Joshua asked the Lord about the defeat, the Lord responded, "Israel has sinned; they have transgressed my covenant that I commanded them; they have taken some of the devoted things; they have stolen and lied and put them among their own belongings." The effect of one man's sin was felt among the assembly of God's people and to some degree the responsibility of God's people in his eyes.
One thing this episode expresses is the connection of God's people to each other. Every member of the body of Christ is connected to each other (1 Corinthians 12; Romans 12:14-16). It also teaches us the far-reaching effects of one man's sin and disobedience. Our personal sins do not just affect us, but others around us. They cause setbacks and brings discipline (Hebrews 12:5-11). Another truth this episode teaches us is that sometimes our greatest temptations come in the midst of our greatest victories.
In Achan's case, as with Ananias and Sapphira (Acts 5:1-11), the discipline and judgment of the Lord was quick and severe to demonstrate the importance of complete obedience. Yes, the people of God eventually defeated Ai but not after the setback of losing the battle, the loss of 36 fighting men, and the discouragement that began to settle in because of losing the battle (Joshua 7:5).
I am always struck to the core when I read this story of the OT. God had already given his people the Promised Land, yet battles still had to be fought. As long his people were obedient to his instructions they won the battle. Obedience to the Lord's instructions (his Word) is the condition for victory. It doesn't mean there will not be temptations or battles to fight, but it does mean that the Lord has given us the means by which we can experience the victory he has already given to us.
May our hearts be in tune with the Holy Spirit today as we live for Jesus walking in obedience to the Father's will just like Jesus did (John 17:4).