The Works Of Martin Luther, Vol VI, Preface To The Epistle To The Romans
-Outwardly you keep the law with works out of fear of punishment or love of gain. Likewise you do everything without free desire and love of the law; you act out of aversion and force. You'd rather act otherwise if the law didn't exist. It follows, then, that you, in the depths of your heart, are an enemy of the law.
-In chapter 7, St. Paul says, "The law is spiritual." What does that mean? If the law were physical, then it could be satisfied by works, but since it is spiritual, no one can satisfy it unless everything he does springs from the depths of the heart. But no one can give such a heart except the Spirit of God, who makes the person be like the law, so that he actually conceives a heartfelt longing for the law and henceforward does everything, not through fear or coercion, but from a free heart. Such a law is spiritual since it can only be loved and fulfilled by such a heart and such a spirit. If the Spirit is not in the heart, then there remain sin, aversion and enmity against the law, which in itself is good, just and holy.
- You must get used to the idea that it is one thing to do the works of the law and quite another to fulfill it. The works of the law are every thing that a person does or can do of his own free will and by his own powers to obey the law. But because in doing such works the heart abhors the law and yet is forced to obey it, the works are a total loss and are completely useless.
- But to fulfill the law means to do its work eagerly, lovingly and freely, without the constraint of the law; it means to live well and in a manner pleasing to God, as though there were no law or punishment. It is the Holy Spirit, however, who puts such eagerness of unconstained love into the heart, as Paul says in chapter 5. But the Spirit is given only in, with, and through faith in Jesus Christ, as Paul says in his introduction. So, too, faith comes only through the word of God, the Gospel, that preaches Christ: how he is both Son of God and man, how he died and rose for our sake. Paul says all this in chapters 3, 4 and 10.
-- it is only unbelief which sins and exalts the flesh and brings desire to do evil external works.
-- That is why only unbelief is called sin by Christ, as he says in John, chapter 16, "The Spirit will punish the world because of sin, because it does not believe in me." Furthermore, before good or bad works happen, which are the good or bad fruits of the heart, there has to be present in the heart either faith or unbelief, the root, sap and chief power of all sin. That is why, in the Scriptures, unbelief is called the head of the serpent and of the ancient dragon which the offspring of the woman, i.e. Christ, must crush, as was promised to Adam (cf. Genesis 3).
-- Faith is a work of God in us, which changes us and brings us to birth anew from God (cf. John 1).
-- Ask God to work faith in you; otherwise you will remain eternally without faith, no matter what you try to do or fabricate.
-- Neither nature nor free will nor our own powers can bring about such a justice, for even as no one can give himself faith, so too he cannot remove unbelief. How can he then take away even the smallest sin?
In chapters 9, 10 and 11, St. Paul teaches us about the eternal providence of God. It is the original source which determines who would believe and who wouldn't, who can be set free from sin and who cannot. Such matters have been taken out of our hands and are put into God's hands so that we might become virtuous. It is absolutely necessary that it be so, for we are so weak and unsure of ourselves that, if it depended on us, no human being would be saved. The devil would overpower all of us. But God is steadfast; his providence will not fail, and no one can prevent its realization. Therefore we have hope against sin.