Melancthon says of these first lectures by Luther on the Psalms and the Epistle to the Romans, that after a long and dark night, a new day was now seen to dawn on Christian doctrine. In these lectures Luther pointed out the difference between the law and the gospel. He refuted the errors, then predominant in the Church and schools, the old teaching of the Pharisees, that men could earn forgiveness by their works, and that mere outward penance would justify them in the sight of God. Luther called men back to the Son of God; and just as John the Baptist pointed to the Lamb of God who bore our sins, so Luther showed how, for his Son's sake, God in His mercy will forgive us our sins, and how we must accept such mercy in faith.
In fact, the whole groundwork of that Christian faith on which the inner life of the Reformer rests, for which he fought, and which gave him strength and fresh courage for the fight, lies already before us in his lectures and sermons during those years, and increases in clearness and decision. The 'new day' had, in reality, broken upon his eyes. That fundamental truth which he designated later as the article by which a Christian Church must stand or fall, stands here already firmly established, before he in the least suspects that it would lead him to separate from the Catholic Church, or that his adopting it would occasion a reconstruction of the Church. The primary question around which everything else centred, remained always this--how he, the sinful man, could possibly stand before God and obtain salvation. With this came the question as to the righteousness of God; and now he was no longer terrified by the avenging justice of God, wherewith He threatens the sinner; but he recognised and saw the meaning of that righteousness declared in the gospel (Rom. i. 17, iii. 25), by which the merciful God justifies the faithful, in that He of His own grace re-establishes them in His sight, and effects an inward change, and lets them thenceforth, like children, enjoy His fatherly love and blessing. Luther, in teaching now that justification proceeds from faith, rejects, above all, the notion that man by any outward acts of his own can ever atone for his sins and merit the favour of God. He reminds us, moreover, with regard to moral works especially, that good fruits always presuppose a good tree, upon which alone they can grow, and that, in like manner, goodness can only proceed from a man, if and when, in his inward being, his inward thoughts, tendencies, and feelings, he has already become good; he must be righteous himself, in a word, before he works righteousness. But it is faith, and faith alone, which in the inward man determines real communion with God. Then only, and gradually, can a man's own inner being, trusting to God, and by means of His imparted grace, become truly renovated and purged from sin. Had Luther, indeed, made salvation depend on such a righteousness, derived from a man's own works, as should satisfy the holy God, the very consciousness of his own sins and infirmities would have made him despair of such salvation. Moreover, all the working of the Holy Spirit, and His gifts in our hearts, presuppose that we are already participators of the forgiving mercy and grace of God, and are received into communion with Him. To this, as Luther teaches after St. Paul, we can only attain through faith in the joyful message of His mercy, in His compassion, and in His Son, whom He has sent to be our Redeemer. Thus he speaks of faith, even in his earliest notes on the Psalter, as the keystone, the marrow, the short road. The worst enemy, in his sight, is self-righteousness; he confesses having had to combat it himself.