Most believers are quite familiar with Ephesians 6:14-17, which speaks of the Armor of God. For reminder's sake, here it is:
Stand therefore, having girded your waist with truth, having put on the breastplate of righteousness, and having shod your feet with the preparation of the gospel of peace; above all, taking the shield of faith with which you will be able to quench all the fiery darts of the wicked one. And take the helmet of salvation, and the sword of the Spirit, which is the word of God.
As I was studying the words, I realized that the first three pieces of armor are already in place. They were provided to us at the moment of redemption, when we are born again in Messiah. We are already armed with the truth (by which we realized Yeshua IS our savior), the breastplate of righteousness (Yeshua made us righteous), and our feet have been prepared with the good news of peace in Messiah. At the moment our justification, we were armed with good armor!
The Bible instructs us then, having been armed thus far, to take up the remaining pieces. We must arm ourselves with that shield of faith day by day, because those fiery darts are constantly aimed at us. The helmet of salvation is a picture of renewing our mind and taking every thought captive to Yeshua (Romans 2:12, 2 Corinthinans 10:5). And finally, the sword - the Word of God - is our spiritual bread that sustains and arms us. These three pieces are available to us as we are sanctified (a lifelong process), but we must actively take them up. We need them as we work out our salvation (Philippians 2:12).
Notice that there is no armor for our backs. I believe it is because God does not want us to retreat from the battle, and also because He has got our back!
I find it interesting that spiritual armor was not just a clever idea made up by Paul in Ephesians. He was a Torah scholar, and was well familiar with the concept. Here is a passage from Isaiah 59, which is clearly foreshadowing the Messiah:
Then the Lord saw it [man's sinfulness] and it displeased Him
That there was no justice. He saw that there was no man,
And wondered that there was no intercessor;
Therefore His own arm brought salvation for Him;
And His own righteousness, it sustained Him.
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,
Another piece of the Ephesians armor can be found in Isaiah 52:7:
How beautiful upon the mountains
Are the feet of him who brings good news,
Who proclaims peace,
Who brings glad tidings of good things,
Who proclaims salvation,
Who says to Zion,
“Your God reigns!”
In closing, let's go back to the beginning of Ephesians 6 and be reminded of just Who is in charge and who we are battling:
Finally, my brethren, be strong in the Lord and in the power of His might. Put on the whole armor of God, that you may be able to stand against the wiles of the devil. For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age,against spiritual hosts of wickedness in the heavenly places.