Ephesians 6:16 ASV

Paul was in prison when he wrote the letter to the Ephesians (see verse 20), and he may have been guarded by Roman soldiers, so he knew all about how these soldiers were equipped. Their shields were about four feet tall and rectangular, made of wood. The wood was covered with leather, which could be soaked in water so that the shield would become impervious to the flaming arrows shot by the enemy.

Why were the shields rectangular instead of round? When the Roman army marched against its enemy, each soldier could fit his shield flush against the shield of the soldier to the right and to the left, forming an almost impenetrable wall. The soldiers could march forward in lock step. As long as each soldier was well equipped, played his part, and stayed connected to the rest of the line, the army could advance.

The church is not too different today. The shield of faith works best when it is connected to the faith of other believers. When one believer lets go of his faith, he not only leaves himself open to Satan's attacks, but also may cause harm to other believers who are close by. The church advances best when each of us, you and me, holds fast to our faith and works together for God's glory.