Invoking the Word of God is essential in battling the evil one.
And I heard a loud voice in heaven, saying, 'Now the salvation and the power and the kingdom of our God and the authority of his Christ have come, for the accuser of our brothers has been thrown down, who accuses them day and night before our God. And they have conquered him by the blood of the Lamb and by the word of their testimony, for they loved not their lives even unto death.'" (Rev. 12:10-11 ESV).
Satan is an accuser and a deceiver. In both cases his weapons are words, which is why we must overcome him with the word of our testimony.
In other words, it is through our belief in the gospel and our confidence in the power of Jesus Christ that we can stand secure in the face of Satan's lies and accusations. And it is by the truth of the word of God—believed on and hoped in even unto death—that we can expose and destroy the deceptions of the deceiver. This is how we do battle, with the sword of the Spirit which is the word of God. Read more