Given his Jewish upbringing, Paul’s thinking is continually informed by Old Testament teaching, especially as he unpacks the armor of God in Ephesians 6:10–20. Still, Paul almost certainly has in mind as well the armor of the Roman soldiers he saw every day throughout the empire. Thus, when appropriate, we will note how this armor’s construction illustrates the apostle’s teaching.
Furthermore, the way Paul describes this armor shows us that we cannot hope, in our own might, to stand against the Devil. Grammatically, standing fast follows the donning of the armor in 6:14–17. We stand “having put on” and “having fastened” this spiritual armor first (v. 14). Putting on Christ and His graces is the first step to success in spiritual warfare — in the subjugation of our enemies (Rom. 13:14).
Ancient Roman soldiers wore a leather apron to protect their thighs from the attacks of their foes, and this piece of armor is the counterpart to the “belt of truth” (Eph. 6:14). Without God’s truth we have no true support — we remain completely vulnerable and are left, effectively, with no legs to stand on. If we lose the truth of the gospel (1:13; 4:21, 24; 5:9), we have the bottom cut right out from under us, rendering us unable to withstand the assaults of false doctrine, half-truths, and other deviations from the Lord’s revelation. According to Isaiah 11:5, the Messiah wears a belt of righteousness and faithfulness. Knowing the truth of the gospel, we see that God has been faithful to His promise to declare us righteous in Christ.
Christians must also wear the breastplate of righteousness, the part of the soldier’s armor protecting his vital organs from arrows and other blows. Commentators disagree as to whether the righteousness in view here is the imputed righteousness of Christ by which we are justified (2 Cor. 5:21) or the ethical righteousness that we practice and so reveal the authenticity of our faith to the world (James 2:14–26). It may be best to see the apostle as speaking, in some sense, of both. Understanding that God has declared us righteous by faith alone encourages us to repent and keep fighting after we fall, confident that He has covered our failures to follow His command. Practicing righteousness makes us better able to resist the sins that would detract us from efficiency and effectiveness in our mission. Today, people want to deny the existence of absolute truth and inst