Finally, be strong in the Lord, and in the strength of His might. Put on the whole armor of God, that you may be able to stand against the schemes of the devil. For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. Therefore, take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand firm. Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness, and, as shoes for your feet, having put on the readiness given by the gospel of peace. In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one; and take the helmet of salvation, and the sword of the Spirit, which is the word of God, praying at all times in the Spirit, with all prayer and supplication.Tragically, when many Christians talk about "spiritual warfare," prayer is rarely in the conversation.
Though it is true that Jesus Himself regularly rebuked and cast out demons (e.g. Mark 1:23-27, 34, 39, etc.), and that He gave authority to the twelve apostles (Mark 3:14-15*), we must be careful to not make the narrative sections of the Bible normative.
Unfortunately, many well-intentioned but poorly-informed Christians read a passage like Mark 3:14-15 or Luke 9:1-3 and believe that we too have been commissioned by Christ with power and authority over all demons and diseases, even though there are zero commands for 'non-apostles' in the NT letters to go around rebuking, binding, and casting out demons.
Rather, we find ourselves reading things like, "Resist [the devil], firm in the faith" (1 Peter 5:9, my translation). Or here in Ephesians 6, the clearest passage in the NT letters, we are called to "put on" and "take up" the whole armor of God.
Rather than providing an exposition of each accoutrement of armor, it will suffice for us simply to sum up Paul's teaching by saying that we need to apply the gospel - in all of its glorious aspects - to our lives.
In Ephesians 4:24, we "put on" the new man by having the Spirit renew our minds.** Here, we "put on" the gospel in and by "praying in the Spirit."***
In other words, just as we can't live the Christian life without the Spirit's power, neither can we do 'spiritual' warfare without the Spirit's presence.
But what does it mean to pray "in the Spirit"? It unlikely refers to praying in tongues. More likely, it has to do with praying "in the sphere" of the Spirit.*** That is, we pray in His neighborhood. And His neighborhood is simply the gospel of Christ. This fits the context here, as well as other passages such as 3:5-6, where the Spirit enables us to "get" the riches of the gospel that God has for us in Christ (cf. the "Spirit who reveals" in 1:17).
To be mindful of Christ and to be full of the gospel (cf. 5:18) is to be "in the Spirit."****
So let's never separate spiritual warfare from the Spirit, whose weapon to fight against Satan and his foes is "the Word of God." As we pray the gospel, we put a sword in His sovereign hands, which protects us from all of Satan and his deceitful schemes.
This is New Testament spiritual warfare. It's all about the gospel of Christ. And it's all about prayer.
So let's pray for the Spirit to apply the gospel to our hearts (cf. 3:16-17) and minds (cf. 4:23), so that we might be equipped and empowered to "stand strong in this evil day."
Oh how we need to "get" the gospel. Let's pray that the Spirit would help us really get it. Otherwise we are easy pickings for the adversary of our souls.
In Christ, and for His glory to the ends of the earth,
* Mark 3:14-15 - "And [Jesus] appointed twelve (whom He also named apostles) so that they might be with Him and that He might send them out to preach and have authority to cast out demons." (my translation)
** The ESV translation is a good literal translation, but seems to miss Paul's Pneumatology in Ephesians. The Spirit is central to the Christian life, from regeneration (2:5) to sealing (1:13-14). He maintains our unity (4:3), empowers our obedience (5:18), and makes us long for the day of redemption (4:30). In 4:24, He is the One who renews our mind, enlightening the eyes of our hearts to better know God and His ways (cf. 1:17-18).
*** Unfortunately, the NIV translates the participle "praying" as if it were a new command or imperative ("And pray in the Spirit"). Though possible, it is more likely that this participle is the means by which the Christian puts on the whole armor of God enumerated by Paul in the previous verses ("Put on...take up...by praying...").
**** For Greek nerds, I take this the dative preposition "in" to be a dative of sphere.
***** The participle here can be the result. That is, when we saturate our services with the gospel, the congregation (the verb is plural) is "filled in/with the Spirit." This is Graham Cole's exegetical conclusion in his "He who Gives Life: The Doctrine of the Holy Spirit." I take it as both/and. When we are filled with the Spirit, we sing and give thanks. But singing and giving thanks and having the gospel saturate our service provides a means of being filled collectively with the Spirit.