The shield of faith in the metaphorical armor of God is the most movable and flexible part of the armor. Like moving the shield, using faith requires action. Solders using the spiritual shield of faith gain strength as they join with other like-minded solders for God. The whole is bigger than the sum of the parts in that the faith, interacting with other Christians, produces a powerful defense against Satan. Like a physical shield, faith could be considered armor for our armor, our foundation and assurance of God's ultimate protection and evidence or conviction of things not yet seen, giving us the inspiration to live the life God has directed us to live. God gave Abraham the promise from the very beginning that He would protect him from his enemies. This promise would extend to his offspring, including us. The metaphor of the protective shield is used 40 times in the Old Testament. The leather cover of a physical shield requires oil applied to it every day, analogous to the daily application of God's Holy Spirit on our spiritual shields by means of daily prayer and Bible study. As water is applied to physical shields to quench fiery darts, our spiritual shields should be saturated with water, another emblem of God's Spirit. As God's spiritual soldiers, we have the responsibility to interlock our shields protecting one another, relying upon Jesus Christ as our metaphorical buckler.