From the Word
For whatever is born of God overcomes the world; and this is the victory that has overcome the world—our faith.
1 John 5:4, RSV
It is, indeed, saying very much for the Christian faith to attribute to it such power over the devil and the world — a power transcending all human ability. It requires an agency greater and higher than human strength to triumph over the devil, especially in the perplexing conflicts of conscience, when he vexes and tortures the heart with terror of God’s wrath in the attempt to drive us to despair. At such times all our works must immediately sink out of sight, leaving no help or victory except the faith that clings to the word of Christ the Lord, believing that, for the sake of his beloved Son, God will be merciful and will not condemn us for our sins and unworthiness, if we believe in him. Such faith as this stands fast and gains the victory; neither the devil, nor the gates of hell can prevail against it.
The same is true in all temptations. Before we can resist and overcome, we must have faith to believe that through Christ we have remission of sins and the favor of God; that God gives us help and strength to enable us to stand in the conflict and successfully resist the devil, the world, the flesh, and death; that we obtain the victory by the divine power of the Holy Spirit, lacking whose help we all would be far too weak to win. Without faith, we are under the power of the devil and sin, being subject to them by natural birth. We can be liberated in no other way than through faith in Christ.
The faith which believes Jesus is the Son of God is the true, triumphant sort. It is an invincible power wrought in the hearts of Christians by the Holy Spirit. It is a sure knowledge, that does not gaze and vacillate hither and thither according to its own thoughts. It apprehends God in Christ the Son sent from heaven, through whom God reveals his will and his love and transfers us from sin to grace, from death to a new, eternal life; a refuge and trust that relies, not upon its own merit and worthiness, but upon Christ the Son of God, and in his might and power battles against the world and the devil. It is a living, active power, ever followed by victories and other appropriate fruits.
Luther, Martin, and John Sander. Devotional Readings from Luther’s Works for Every Day of the Year. Augustana Book Concern, 1915, pp. 164–65.