The book, indeed, surpasses all his previous German writings in volume, as well as all his Latin and German ones in clearness, richness and the fundamental importance of its content. In comparison with the prevalent urging of self-elected works of monkish holiness, which had arisen from a complete misunderstanding of the so-called evangelical counsels (comp.
esp. Matthew 19:16-22) and which were at that time accepted as self-evident and zealously urged by the whole church, Luther's argument must have appeared to all thoughtful and earnest souls as a revelation, when he so clearly amplified the proposition that only those works are to be regarded as good works which God has commanded, and that therefore, not the abandoning of one's earthly calling, but the faithful keeping of the Ten Commandments in the course of one's calling, is the work which God requires of us. Over against the wide-spread opinion, as though the will of God as declared in the Ten Commandments referred only to the outward work always especially mentioned, Luther's argument must have called to mind the explanation of the Law, which the Lord had given in the Sermon on the Mount, when he taught men to recognize only the extreme point and manifestation of a whole trend of thought in the work prohibited by the text, and when he directed Christians not to rest in the keeping of the literal requirement of each Commandment, but from this point of vantage to inquire into the whole depth and breadth of God's will --positively and negatively -- and to do His will in its full extent as the heart has perceived it. Though this thought may have been occasionally expressed in the expositions of the Ten Commandments which appeared at the dawn of the Reformation, still it had never before been so clearly recognized as the only correct principle, much less had it been so energetically carried out from beginning to end, as is done in this treatise. Over against the deep-rooted view that the works of love must bestow upon faith its form, its content and its worth before God, it must have appeared as the dawn of a new era (Galatians 3:22-25)when Luther in this treatise declared, and with victorious certainty carried out the thought, that it is true faith which invests the works, even the best and greatest of works, with their content and worth before God.
This proposition, which Luther here amplifies more clearly than ever before, demanded nothing less than a breach with the whole of prevalent religious views, and at that time must have been perceived as the discovery of a new world, though it was no more than a return to the clear teaching of the New Testament Scriptures concerning the way of salvation. This, too, accounts for the fact that in this writing the accusation is more impressively repelled than before, that the doctrine of justification by faith alone resulted in moral laxity, and that, on the other hand, the fundamental and radical importance of righteousness by faith for the whole moral life is revealed in such a heart-refreshing manner. Luther's appeal in this treatise to kings, princes, the nobility, municipalities and communities, to declare against the misuse of spiritual powers and to abolish various abuses in civil life, marks this treatise as a forerunner of the great Reformation writings, which appeared in the same year (1520), while, on the other hand, his espousal of the rights of the "poor man" -- to be met with here for the first time --shows that the Monk of Witttenberg, coming from the narrow limits of the convent, had an intimate and sympathetic knowledge of the social needs of his time. Thus he proved by his own example that to take s stand in the center of the Gospel does not narrow the vision nor harden the heart, but rather produces courage in the truth and sympathy for all manner of misery.
Luther's contemporaries at once recognized the great importance of the Treatise, for within the period of seven months it passed through eight editions; these were followed by six more editions between the years of 1521 and 1525; in 1521 it was translated into Latin, and in this form passed through three editions up to the year 1525; and all this in spite of the fact that in those years the so-called three great Reformation writings of 1520 were casting all else into the shadow. Melanchthon, in a contemporaneous letter to John Hess, called it Luther's best book. John Mathesius, the well-known pastor at Joachimsthal and Luther's biographer, acknowledged that he had learned the "rudiments of Christianity" from it.
Even to-day this book has its peculiar mission to the Church. The seeking after self-elected works, the indolence regarding the works commanded of God, the foolish opinion, that the path of works leads to God's grace and good-will, are even to-day widely prevalent within the kingdom of God. To all this Luther's treatise answers: Be diligent in the works of your earthly calling as commanded of God, but only after having first strengthened, by the consideration of God's mercy, the faith within you, which is the only source of all truly good works and well-pleasing to God.
