It's interesting that when Paul admonishes the church to put on the whole armor of God, he leaves out two items.
Paul was no doubt drawing his analogy from Isaiah 59:17 which reads, "For He put on righteousness as a breastplate, and a helmet of salvation on His head; He put on the garments of vengeance for clothing, and was clad with zeal as a cloak."
So we see here two of the articles which Paul used in referring to the Armor of God, namely, the breastplate of righteousness and the helmet of salvation.
But there are two additional articles that Paul didn't include: the garments of vengeance and the cloak of zeal.
Now we know that vengeance belongs to the Lord (Deut. 32:35, Heb. 10:30, Rom. 12:19) so that explains why the garments of vengeance are not ours to wear, but Christ's alone.
But we as Christians are commanded by Christ to put on the cloak of zeal!
Revelation 3:19, "As many as I love, I rebuke and chasten. Therefore be zealous and repent."
Galatians 4:18, "But it is good to be zealous in a good thing always, and not only when I am present with you."
Titus 2:14, "who gave Himself for us, that He might redeem us from every lawless deed and purify for Himself His own special people, zealous for good works."
But there's another side to zeal...a darker side. Perhaps Paul, wanting to keep on the safe side, left out the cloak of zeal because of it's counterpart, the cloak of ignorant zeal. About this dangerous form of zeal, with which he was sadly very familiar, Paul writes:
Acts 22:3,4, "I am indeed a Jew, born in Tarsus of Cilicia, but brought up in this city at the feet of Gamaliel, taught according to the strictness of our fathers’ law, and was zealous toward God as you all are today. I persecuted this Way to the death, binding and delivering into prisons both men and women,"
Romans 10:2, "For I bear them witness that they have a zeal for God, but not according to knowledge."
Galatians 1:14, "And I advanced in Judaism beyond many of my contemporaries in my own nation, being more exceedingly zealous for the traditions of my fathers."
So, Christians, when putting on the Armor of God, don't forget your cloak of zeal! But be sure it's a zeal according to knowledge.