Charles Ellicott Commentary Ephesians 6:14

"Stand therefore, having girded your loins with truth, and having put on the breastplate of righteousness," — Ephesians 6:14 (ASV)

Your loins girded about with truth, and wearing the breastplate of righteousness.—There is an obvious reference here to two passages of Isaiah (Isaiah 11:5; Isaiah 59:17): Righteousness shall be the girdle of his loins, and He put on righteousness as a breastplate. Truth and righteousness are virtually identical, or at least inseparable. Therefore, they are compared to the strong belt and the breastplate continuous with it, forming together the armor of the body. Perhaps “truth” is taken as the belt because it is the one bond of both society and individual character. But it is in the two together that individuals stand “armed strong in honesty.” In 1 Thessalonians 5:8, the metaphor is different and perhaps less exact. There the breastplate is the breastplate of faith and love—which here is the shield.

On verses 14-17:

In this magnificent passage, while it would be unreasonable to look for formal and systematic exactness, it is clear that (as usual in St. Paul’s most figurative passages) a distinct line of thought runs through the whole.

1. Thus, the order in which the armor is enumerated is clearly the order in which the Roman soldier's armor was actually put on. It nearly corresponds with the invariable order in which Homer describes over and over again the arming of his heroes: first the belt and the corselet, which met and together formed the body armor; then the sandals; next the shield; and after this (because the strap of the great shield could hardly pass over the helmet), the helmet itself. Then the soldier was armed and only had to take up the sword and spear. It is curious to note that St. Paul omits the spear (the pilum of the Roman soldier)—exactly that part of his equipment which, when on guard indoors, the soldier would not likely carry.
2. Again, since to put on the armor of light is to put on the Lord Jesus Christ, it follows that the various parts of the defensive armor are the various aspects of the image of the Lord Jesus Christ. Therefore, they are properly His and are appropriated by us through His gift. Thus, the “righteousness” is clearly the righteousness of Christ, realized in us ; the sandals, which give firm footing, are the gospel of our peace in Him; the salvation is His salvation worked out in us. Only the sword is in no sense our own: it is the Word of God, wielded by us, but in itself living and powerful and sharp (Hebrews 4:12).