Ephesians 6: 11-18 describes the Armor of God. In this passage, Paul isn’t giving us an option of whether or not we need to put on the Armor, he’s stating that we need to put on the armor because we’re in a spiritual battle. This isn’t optional. Soldiers in a battle that are untrained and without armor are generally known as casualties.
Paul lists the pieces we need to use and although he’s chained to a Roman guard, these idioms go back to the Old Testament.
Being chained to the guard may have inspired Paul to write this passage and remind him of what he would have read in the Law and the Prophets.
Order ye the buckler and shield, and draw near to battle.
Harness the horses; and get up, ye horsemen, and stand forth with your helmets; furbish the spears, and put on the brigandines (coat of mail).
Belt of Truth
And righteousness shall be the girdle of his loins, and faithfulness the girdle of his reins.
Helmet of Salvation and Breastplate of Righteousness
For he put on righteousness as a breastplate, and an helmet of salvation upon his head; and he put on the garments of vengeance for clothing, and was clad with zeal as a cloke..
Feet shod with the Preparation of the Gospel of Peace
7 How beautiful upon the mountains are the feet of him that bringeth good tidings, that publisheth peace; that bringeth good tidings of good, that publisheth salvation; that saith unto Zion, Thy God reigneth!
Sheild of Faith
Every word of God is pure: he is a shield unto them that put their trust in him.
Our soul waiteth for the LORD: he is our help and our shield.
Sword of the Spirit
29 Happy art thou, O Israel: who is like unto thee, O people saved by the LORD, the shield of thy help, and who is the sword of thy excellency! and thine enemies shall be found liars unto thee; and thou shalt tread upon their high places.
15 And out of his mouth goeth a sharp sword, that with it he should smite the nations: and he shall rule them with a rod of iron: and he treadeth the winepress of the fierceness and wrath of Almighty God.
By going through the Old Testament we can see that the Lord is in each piece of armor. By putting on the armor, we put our faith in God and not in ourselves.