From Kevin DeYoung at The Gospel Coalition:
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.”
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.
So when Satan whispers, “Can God really forgive you? Can your sins be washed away?” you can answer confidently: “There is now no condemnation for those who are in Christ Jesus. For the law of the Spirit of life has set you free in Christ Jesus from the law of sin and death.” (Rom. 8:1-2).
When the Devil says your situation is hopeless, when he calls you an addict and says you can’t change, you can reply: “Those who are in the flesh cannot please God. You, however, are not in the flesh but in the Spirit, if in fact the Spirit of God dwells in you. Anyone who does not have the Spirit of Christ does not belong to him.” (Rom. 8:8-9).
And when Satan suggests that it must not matter then how we live, that grace and freedom are an excuse for license, we must answer: “For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live” (Rom. 8:13).
And when our Enemy points to our suffering and says, “Look, God cannot be trusted. Surely, there is no use in serving this Master” we will inform him that we “consider that our present sufferings are not worth comparing with the glory that will be revealed in us” (Rom. 8:18).
And if Satan should tempt us to believe that God is singling us out for pain, we will remind him that “the whole creation has been groaning together in the pains of childbirth until now” (Rom. 8:22).
If he spreads the lie that our trials will be the end of us, that God can no longer help us, we will declare, “And we know that for those who love God all things work together for good” (Rom. 8:28).
And when he shows us our weakness, when he points to the failures of the church, when he accuses us of having let God down and makes us doubt the power of the gospel and the ultimate triumph of the saints, when he comes at us with words and all the weapons of the world, we will stand our ground with a defiant shout: “No, in all these things we are more than conquerors through him who loved us. For I am sure that neither death nor life, nor angels nor rulers, nor things present nor things to come, nor powers, nor height nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord” (Rom. 8:37-39).
Satan is hell bent on destroying the church. He breathes fiery accusations like a dragon and hisses deception like a serpent. He is in pursuit of the woman and her children. But the salvation and the power and the kingdom belong to God and to Christ our King. And we shall overcome the devil, by the blood of the Lamb and by the word of our testimony.