Charles Hodge on Ephesians 6:17

V. 17. The most ornamental part of ancient armour, and scarcely less important than the breast-plate or the shield, was the helmet. The Christian, therefore, is exhorted to take τὴν περικεφαλαίαν τοῦ σωτηρίου, the helmet of salvation. According to the analogy of the preceding expressions, "the breast-plate of righteousness," and "shield of faith," salvation is itself the helmet. That which adorns and protects the Christian, which enables him to hold up his head with confidence and joy, is the fact that he is saved. He is one of the redeemed, translated from the kingdom of darkness into the kingdom of God’s dear Son. If still under condemnation, if still estranged from God, a foreigner and alien, without God and without Christ, he could have no courage to enter into this conflict. It is because he is a fellow-citizen of the saints, a child of God, a partaker of the salvation of the Gospel, that he can face even the most potent enemies with confidence, knowing that he shall be brought off more than conqueror through him that loved him; Rom. 8, 37. When in 1 Thess. 5, 8, the apostle speaks of the hope of salvation as the Christian’s helmet, he presents the same idea in a different form. The latter passage does not authorize us to understand, in this place, "helmet of salvation" as a figurative designation of hope. The two passages though alike are not identical. In the one salvation is said to be our helmet, in the other, hope; just as in one place "faith and love" are said to be our breast-plate, and in another, righteousness.

The armour hitherto mentioned is defensive. The only offensive weapon of the Christian is "the sword of the Spirit." Here τοῦ πνεύματος cannot be the genitive of apposition. The Spirit is not the sword; this would be incongruous, as the sword is something which the soldier wields, but the Christian cannot thus control the Spirit. Besides, the explanation immediately follows, which is the word of God. "The sword of the Spirit" means the sword which the Spirit gives. By the ῥη̂μα Θεοῦ is not to be understood the divine precepts, nor the threatenings of God against his enemies. There is nothing to limit the expression. It is that which God has spoken, his word, the Bible. This is sharper than any two-edged sword. It is the wisdom of God and the power of God. It has a self-evidencing light. It commends itself to the reason and conscience. It has the power not only of truth, but of divine truth. Our Lord promised to give to his disciples a word and wisdom which all their adversaries should not be able to gainsay or resist. In opposition to all error, to all false philosophy, to all false principles of morals, to all the sophistries of vice, to all the suggestions of the devil, the sole, simple, and sufficient answer is the word of God. This puts to flight all the powers of darkness. The Christian finds this to be true in his individual experience. It dissipates his doubts; it drives away his fears; it delivers him from the power of Satan. It is also the experience of the church collective. All her triumphs over sin and error have been effected by the word of God. So long as she uses this and relies on it alone, she goes on conquering; but when any thing else, be it reason, science, tradition, or the commandments of men, is allowed to take its place or to share its office, then the church, or the Christian, is at the mercy of the adversary. Hoc signo vinces—the apostle may be understood to say to every believer and to the whole church.