What the faith is, which justifies us before God.
Our adversaries think, that faith consists in a knowledge of, or an acquaintance with, the history of Christ; hence they teach that we can believe, even when sunk in moral sin. Accordingly they neither know nor say anything of the true Christian faith, by which, Paul invariably says, we are justified before God. For those that are just and holy in the sight of God, are surely not in mortal sin. Therefore the faith, which justifies us before God, consists not only in a knowledge of the history of Christ, his birth, sufferings, &c., (for this even the devils have,) but it is the conviction, the fixed, firm confidence of our hearts, fully trusting in the promises of God, which, without our merit, offer us the remission of sin, grace, and full salvation, through Christ the Mediator. And that no one may suppose it to be a mere historical knowledge, I add that faith is the acceptance of this treasure with our whole heart, and this is not our own act, present or gift, our own work or preparation; but the heart must be assured and fully trust, that God presents and gives to us, and not we to him; that he pours out upon us the whole treasure of grace in Christ. (Henkel Translation, p. 166).