“Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness,” (Ephesians 6:14 (ESV)
The next piece of the believer’s armor is the breastplate of righteousness. For the ancient Roman soldier, the breastplate (θώραξ; thorax) was the armor which covered the body from the neck to the thighs. It consisted of two parts: one part covering the front and the other the back.
The breastplate consisted of a tough, sleeveless piece of leather or heavy material with animal horn or hoof pieces sewn on, covering the soldier’s full torso. It protected the soldier’s heart and other vital organs.
The Apostle Paul associates the breastplate with righteousness. The question arises as to what is the meaning of the word righteousness (δικαιοσύνη; dikaiosyne) in this particular context. Is the Apostle Paul referring to the imputed righteousness of Christ or justification (Romans 3:21-26; Philippians 3:1-9) which describes the believer’s position before God in Christ. Or is Paul referring to the believer’s practice of righteousness or sanctification (Ephesians 4-5; Colossians 3-4; I Thessalonians 4:1-12) which is the believer’s ethical righteousness before God and man. Most scholars believe it to be both.
Dr. R. C. Sproul writes, “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.”
A key to our understanding of the text is the phrase having put on (ἐνδύω; endyo) which means to personally dress and clothe oneself. Since the believer in Christ is justified by grace alone, through faith alone in the person and work of Christ alone (Ephesians 1:3-2:9) the text in 6:14 must be referring to the believer’s personal, daily and ethical righteousness.
Dr. John MacArthur writes, “Because righteousness, or holiness, is such a distinctive characteristic of God himself, it is not hard to understand why that is the Christian’s chief protection against Satan and his schemes. As believers faithfully live in obedience to and communion with Jesus Christ, his own righteousness produces in them the practical, daily righteousness that becomes their spiritual breastplate. Lack of holiness, on the other hand, leaves them vulnerable to the great enemy of their souls (cf. Isa. 59:17; 2 Cor. 7:1; 1 Thess. 5:8).”
Believers are justified by grace alone, through faith alone, in Christ alone. However, the evidence of the imputed righteousness of Christ is the practice of ethical righteousness by our lives. Have a blessed day.
Soli deo Gloria!