Ephesians 6:16 says, "In addition to all, taking up the shield of faith with which you will be able to extinguish all the flaming arrows of the evil one." Roman soldiers used several kinds of shields. The kind Paul refers to here (Gk., thureos) was about two-and-a-half feet wide and high, designed to protect the entire body of the soldier. The shield was made of a solid piece of wood and was covered with metal or thick leather.
The faith Paul refers to here is faith in God, which is immeasurably more reliable than practical, everyday faith we live by. And it is far from being blind faith. Faith is only as reliable and helpful as the trustworthiness of its object. The Christian faith is infinitely powerful and because the object of faith is Jesus Christ, it is the infinite God. Our faith never falls because the One in whom our faith is placed never fails.
In New Testament times the tips of arrows would often be wrapped in pieces of cloth that had been soaked in pitch. Just before the arrow was shot, the tip would be lighted and the flaming missile would be shot at the enemy troops. The pitch burned fiercely, and on impact it would splatter flaming bits, igniting anything flammable in its path. In addition to piercing a person's body, such arrows inflicted serious burns on enemy soldiers and destroyed their clothing and gear. The most reliable protection against these flaming missiles was the thureos. Its covering of metal or treated leather would either deflect or extinguish them.
Satan continually bombards God's children with the flaming arrows of immorality, hatred, anger, covetousness, pride, doubt, fear, despair, distrust, and other temptations. Every temptation, either directly or indirectly, tries to get us to doubt or distrust God. The purpose of Satan's missiles is to cause believers to forsake their trust in God, to drive a wedge between the Savior and the saved. Put up the shield of faith and that won't happen to you.