What is the armor of God?

The armor of God comes from the end of Paul’s letter to the Ephesians. After chapters about God’s grace and about living in love, Paul closes with a picture of a soldier. Christian life, he says, is not only peace and fellowship; it also has a fight in it, and God has given us everything we need to stand.

Strength that is not our own

Paul begins not with armor but with strength:

Finally, my brethren, be strong in the Lord, and in the power of his might. Put on the whole armor of God, that ye may be able to stand against the wiles of the devil. For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.
Eph 6:10–12 · King James Version (1769)

The New Geneva Study Bible notes that these are the same words Paul used for the power that raised Jesus from the dead. Believers are told to face dark powers not with their own strength but with that resurrection power. William MacDonald adds that the best soldiers of God are those who know their own weakness and rely on Him alone.

The enemy is real, but he is not first of all other people. MacDonald explains that the real battle is not with wicked philosophers or unbelieving rulers but with evil spiritual beings who press in on every side, and he adds that a Christian should neither be morbidly fascinated by demons nor live in fear of them. John MacArthur points out that Satan’s power over believers was already broken at the cross and the resurrection (Hebrews 2:14), yet the battles with temptation continue in this life until the Lord returns.

The armor is called the armor of God because He prepares and gives it. Matthew Henry notes that it is made to be worn and that we do not take it off until the warfare is finished.

The six pieces of armor

Wherefore take unto you the whole armor of God, that ye may be able to withstand in the evil day, and having done all, to stand. Stand therefore, having your loins girt about with truth, and having on the breastplate of righteousness; And your feet shod with the preparation of the gospel of peace; Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the wicked. And take the helmet of salvation, and the sword of the Spirit, which is the word of God:
Eph 6:13–17 · King James Version (1769)

Paul probably had a Roman soldier in mind, and MacArthur observes that the first three pieces were worn all the time, while the other three were kept ready as soon as the battle began. Here is what each one means.

The belt of truth. The soldier tied up his loose tunic with a belt so that he could fight freely. MacArthur understands truth here as faithfulness to the truth, and MacDonald says we must not only hold the truth but let it hold us in daily life. Henry points to sincerity: there is no true religion without it.
The breastplate of righteousness. It protected the heart and other vital organs. MacDonald writes that every believer is clothed in God’s righteousness (2 Corinthians 5:21) and must also show a pure and honest life, because a clear conscience gives Satan’s arrows nothing to hit.
Shoes of the readiness of the gospel of peace. MacArthur explains that peace with God through Christ gives a firm footing: if God is on our side, He is our strength (Romans 8:31). The New Geneva Study Bible agrees that the picture is of strong sandals that gave a soldier stability. MacDonald reads these shoes as readiness to go out with the good news.
The shield of faith. The large Roman shield covered the whole body. MacArthur says faith here means steady trust in God’s word and promises, which puts out the flaming arrows of temptation and doubt. In Matthew Henry’s words, “Faith is all in all in an hour of temptation.”
The helmet of salvation. MacArthur explains that Satan tries to shake a believer’s assurance with doubt, but salvation is secure in God’s promises (John 10:28). The New Geneva Study Bible notes that the helmet crowns the armor with the awareness that we are saved.
The sword of the Spirit, the word of God. This is the only weapon for attack. MacDonald points to Jesus in the wilderness, who answered each temptation with a fitting word of Scripture (Luke 4:1–13), and MacArthur adds that the sword both turns aside the enemy’s blows and breaks his plans.

Henry also notices that the armor has nothing for the back: nothing protects a soldier who turns and runs.

Prayer and standing firm

Paul does not list prayer among the pieces, yet the passage ends with it:

Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints;
Eph 6:18 · King James Version (1769)

MacDonald calls prayer the air the soldier breathes, the atmosphere in which the whole armor is put on. MacArthur notes that Paul speaks of every kind of prayer, at every time, in the Spirit, with alertness and perseverance, and for all believers. We are not fighting alone.

The weapons are not what we usually reach for. Paul says elsewhere that they are not the weapons of the world:

(For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strongholds;)
2 Cor 10:4 · King James Version (1769)

MacDonald explains that Christians do not fight with wealth, fame or clever speech but with faith in the living God, prayer and obedience to His Word.

What this means for you

The armor is not a technique for defeating Satan on our own. Paul’s call is to stand: to hold the ground Christ has already won, not to go looking for a fight with the devil. What we put on is, in the end, Christ Himself and what He has given: His truth, His righteousness, His peace, His salvation and His word.

In practice that means knowing the Bible, living honestly, trusting God when doubts come and praying often, with other believers beside you. If a fight is hard, you do not need to find more strength in yourself. Be strong in the Lord, put on what He gives, and stand.