While every part of the human body is important, the two parts most critical for life are the heart and the brain. It is no surprise that soldiers past and present have sought to protect these two parts. (Witness modern bullet-proof vests and helmets.) Even ancient soldiers wore breastplates and helmets.

But so did the Messiah—at least in Isaiah’s figurative language. Paul derived his image of the breastplate of righteousness and helmet of salvation from Isaiah’s image of the Messiah (Isaiah 59:17; Ephesians 6:14, 17)—and used the image of a Roman soldier as a ready reference for his readers. So to put on the armor of God was like putting on the Messiah Himself: His truth, righteousness, faithfulness, salvation, and Word (Ephesians 6:14-17). But why the helmet of salvation? How does salvation protect the mind? When Satan tempts us to doubt our salvation and the love of God which secures it, we rely on what we know to be true.

Memorize, in your mind: “There is therefore now no condemnation to those who are in Christ Jesus” (Romans 8:1).

One of the highest and noblest functions of man’s mind is to listen to God’s Word, and so to read his mind and think his thoughts after him.
John R. W. Stott