"'Faith, however, is a divine work within 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, spirit and mind and powers.' (LW 35:370) Faith is wholly and entirely God's work. It is not our own decision, interpretive activity, or construction of meaning. This is the first and most important thing that we have to say about faith. In its significance for people of modernity we cannot rate it too highly. In this regard that Enlightenment is opposed to the Reformation. Reaching a climax in the philosophy of Immanuel Kant, the Enlightenment claimed that with the faculties of pure recollection and pure constuction it could evaluate even the faith. Or there is at least the claim to discover faith in the self, for example as the feeling of absolute dependence. We humans want to make things by ourselves, including faith, or at least we want to assure ourselves of faith. For Luther, however, faith is soley the work of God. Faith encounters us by coming to us. (Gal. 3:23 and 25) We experience it in that we suffer it.
The experience of faith is painful. When Luther spoke about the death of the old Adam, this was no mere metaphor.
He who has not been brought low, reduced to nothing through the cross and suffering, takes credit for works and wisdom and does not give credit to God....He, however, who has emptied himself [cf. Phil. 2:7] through suffering no longer does works but knows that God works and does all things in him...It is this that Christ says in John 3[:7], "You must be born anew." To be born anew, one must consequently first die. (Luther, "Heidelberg Disputation" (1518), LW 31:55The passive righteousness of faith takes place when justifying thinking (metaphysics) and justifying doing (morality), together with the unity of both that some seek, are all radically destroyed. In other words, both metaphysics and morality with their claim to justify our being are brought to nothing by the work of God. God slays, but he does so only to make alive. "The Lord kills and brings to life; He brings down to Sheol and raises up."
-Oswald Bayer, Living by Faith - Justification and Sanctification