THE SWORD OF THE SPIRIT
And take the sword of the Spirit, which is the word of God (Ephesians 6:17).
The Word of God is the only offensive weapon mentioned in the list of armour. Since Paul used rhema instead of logos for 'word' in Ephesians 6:17, I believe Paul is referring to the spoken Word of God. We are to defend ourselves against the evil one by speaking aloud God's Word.
Why is it so important to speak God's Word in addition to believing it and thinking it? Because Satan is a created being, and he doesn't perfectly know what you're thinking. By observing you, he can pretty well tell what you are thinking, just as any student of human behaviour can. And it isn't difficult for him to know what you're thinking if he put the thought in. But he doesn't know what you're going to do before you do it. He can put thoughts into your mind, and he will know whether you buy his lie by how you behave.
Satan can try to influence you by planting thoughts in your head, but he can't read your thoughts. If you're going to resist Satan, you must do so verbally so he can understand you and be put to flight.
You can communicate with God in your mind and spirit because He knows the thoughts and intents of your heart (Hebrews 4:12). Your unspoken communion with God is your private sanctuary; Satan cannot eavesdrop on you. But by the same token, if you only tell Satan with your thoughts to leave, he won't leave because he is under no obligation to obey your thoughts. You must defeat Satan by speaking out. The good news is that most direct attacks occur at night or when you are alone.
One night I woke up absolutely terrified for no apparent reason, and I knew it was an attack from Satan. Without lifting my head from the pillow, I applied the two-step remedy suggested in James 4:7. In the sanctuary of my heart, I submitted to God. Then I was able to resist Satan with one spoken word – Jesus - and the fear was instantly and totally gone. I went back to sleep in complete peace.
Lord, give me courage to take my stand in this world and defeat Satan by speaking Your Word.