Faith is not the human notion and dream that some people call faith. When they see that no improvement of life and no good works follow—although they can hear and say much about faith—they fall into the error of saying, “Faith is not enough; one must do works in order to be righteous and be saved.” This is due to the fact that when they hear the gospel, they get busy and by their own powers create the idea in their heart which says, “I believe;” they take this then to be a true faith. But as it is a human figment and idea that never reaches the depths of the heart, nothing comes of it either, and no improvement follows.
Faith, however, is a divine work in us which changes us and makes us to be born anew of God John 1 [:12-13]. It kills the old Adam and makes us altogether different men, in heart and spirit and mind and powers; and it brings with it the Holy Spirit. Oh, it is a living, busy, active mighty thing, this faith. It is impossible for it not to be doing good works incessantly. It does not ask whether good works are to be done, but before the question is asked, it has already done them, and is constantly doing them. Whoever does not do such good works, however, is an unbeliever. He gropes and looks for faith and good works, but knows neither what faith is nor what good works are. Yet he talks, with many words, about faith and good works.
Faith is a living, daring confidence in God’s grace, so sure and certain that the believer would stake his life on it a thousand times. This knowledge of and confidence in God’s grace makes men glad and bold and happy in dealing with God and with all creatures. And this is the work which the Holy Spirit performs in faith. Because of it, without compulsion, a person is ready and glad to do good to everyone, to serve everyone, to suffer everything, out of love and praise to God who has shown him this grace. Thus it is impossible to separate works from faith, quite as impossible as to separate heat and light from fire. Beware, therefore, of your own false notions and of idle talkers who imagine themselves wise enough to make decisions about faith and good works, and yet are the greatest fools. Pray God that he may work faith in you. Otherwise you will surely remain forever without faith, regardless of what you may think or do. (LW 35, 370-71)