“Put on the full armor of God ... with the belt of truth buckled around your waist, with the breastplate of righteousness in place, and with your feet fitted with the readiness that comes from the gospel of peace. In addition to all this, take up the shield of faith, with which you can extinguish all the flaming arrows of the evil one. Take the helmet of salvation and the sword of the Spirit, which is the word of God” (Ephesians 6:11-17, emphases added).
When we think of the “Armor of God” we all think, of course, of these inspiring verses in Ephesians, but the analogy was not original to Paul. We find in the Book of Isaiah, in the Old Testament, the origin of Paul’s metaphor in verses that the apostle and his readers doubtless knew well.
The first of these verses appears in Isaiah 59: “He put on righteousness like a breastplate, and a helmet of salvation on His head; and He put on garments of vengeance for clothing and wrapped Himself with zeal as a mantle” (Isaiah 59:17). The second group of verses that would have been well-known to Paul is found in Isaiah 11: “He will strike the earth with the rod of his mouth; with the breath of his lips he will slay the wicked. Righteousness will be his belt and faithfulness the sash around his waist”(Isaiah 11:4-5).
Paul does not simply quote the words found in Isaiah about the armor of God, however. Instead, he develops the idea in two ways. First he focuses the elements found in Isaiah. Instead of the 7 items of armor mentioned in the parallel verses in Isaiah, Paul lists 6 items of armor in Ephesians 6, and he adjusts and combines some items in order to do this. He combines the belt of righteousness and sash of faithfulness into the belt of truth, and also combines the only offensive weapons mentioned by Isaiah – the “rod of his mouth” and “breath of his lips” – into the “sword of the Spirit, which is the word of God” (also the only offensive weapon mentioned in Ephesians 6, and clearly the same thing: “rod of his mouth” = “word of God”).
Paul leaves out the “mantle of zeal” and “garments of vengeance” as belonging to God alone (Romans 12:19), but the “breastplate of righteousness” and “helmet of salvation” are identical in both lists. The only items of armor Paul adds to those mentioned explicitly in Isaiah are the “shield of faith” and the shoes of the “gospel of peace,” although the idea for the latter can also be found in Isaiah as well: “How beautiful on the mountains are the feet of those who bring good news, who proclaim peace, who bring good tidings, who proclaim salvation, who say to Zion, ‘Your God reigns!’” (Isaiah 52:7) – a verse which Paul quotes in Romans 10:15.
More important than the minor adjustments to the individual items, Paul’s developed analogy of the armor of God differs from those found in Isaiah by applying the concept of the armor of God Himself to the servant of God – the Christian. He also lifts the weapons of spiritual warfare out of the realm of things that we must somehow put together of our own strength, for the items of armor Paul shows we need so badly are, like salvation itself, the gift of God. When David tried the armor of King Saul he could not use it as he had not “tested” or practiced with it (1 Samuel 17:38-39). Paul reminds his readers that we must not keep these elements of armor on display or locked in some spiritual armory (Ephesians 6:11). The armor of God is something with which we must practice. It is a gift to be used.