I've very much appreciated, recently, Luther's comments on the opening of Galatians 5. As often as I have gone back to his lectures on Galatians, I've not really gone past his discussion up through chapter 4 (contained in Volume 26 of Luther's Works). His treatment of chapters 5 and 6 is found in the next volume of Luther's Works (CPH), and for that reason, silly as it may be, I simply haven't given it the same attention. But already the first few pages have been great:
"‘For freedom Christ has set us free; stand fast therefore’ (Galatians 5:1). That is: ‘Be firm!’ Thus Peter says: ‘Be sober, be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour. Resist him, firm in your faith’ (1 Peter 5:8–9). ‘Do not be smug,’ he says, ‘but be firm. Do not lie down or sleep, but stand.’ It is as though he were saying: ‘Vigilance and steadiness are necessary if you are to keep the freedom for which Christ has set us free. Those who are smug and sleepy are not able to keep it.’ For Satan violently hates the light of the Gospel, that is, the teaching of grace, freedom, comfort, and life. Therefore as soon as he sees it arise, he immediately strives to obliterate it with all his winds and storms. For this reason Paul urges godly persons not to be drowsy and smug in their behavior but to stand bravely in the battle against Satan, lest he take away the freedom achieved for them by Christ.
"Every word is emphatic. ‘Stand fast,’ he says, ‘in freedom.’ In what freedom? Not in the freedom for which the Roman emperor has set us free but in the freedom for which Christ has set us free. The Roman emperor gave — indeed, was forced to give — the Roman pontiff a free city and other lands, as well as certain immunities, privileges, and concessions [or, so it was supposed in Luther’s day; the so-called ‘Donation of Constantine’ has since been shown to be a forgery of the 15th century]. This, too, is freedom; but it is a political freedom, according to which the Roman pontiff with all his clergy is free of all public burdens. In addition, there is the freedom of the flesh, which is chiefly prevalent in the world. Those who have this obey neither God nor the laws but do what they please. This is the freedom which the rabble pursues today; so do the fanatical spirits, who want to be free in their opinions and actions, in order that they may teach and do with impunity what they imagine to be right. This is a demonic freedom, by which the devil sets the wicked free to sin against God and men. We are not dealing with this here although it is the most widespread and is the only goal and objective of the entire world. Nor are we dealing with political freedom. No, we are dealing with another kind, which the devil hates and attacks most bitterly.
"This is the freedom with which Christ has set us free, not from some human slavery or tyrannical authority but from the eternal wrath of God. Where? In the conscience. This is where our freedom comes to a halt; it goes no further. For Christ has set us free, not for a political freedom or a freedom of the flesh but for a theological or spiritual freedom, that is, to make our conscience free and joyful, unafraid of the wrath to come (Matt. 3:7). This is the most genuine freedom; it is immeasurable. When the other kinds of freedom — political freedom and the freedom of the flesh — are compared with the greatness and the glory of this kind of freedom, they hardly amount to one little drop. For who can express what a great gift it is for someone to be able to declare for certain that God neither is nor ever will be wrathful but will forever be a gracious and merciful Father for the sake of Christ? It is surely a great and incomprehensible freedom to have this Supreme Majesty kindly disposed toward us, protecting and helping us, and finally even setting us free physically in such a way that our body, which is sown in perishability, in dishonor, and in weakness, is raised in imperishability, in honor, and in power (1 Cor. 15:42–43). Therefore the freedom by which we are free of the wrath of God forever is greater than heaven and earth and all creation.
"From this there follows the other freedom, by which we are made safe and free through Christ from the Law, from sin, death, the power of the devil, hell, etc. Just as the wrath of God cannot terrify us — since Christ has set us free from it — so the Law, sin, etc., cannot accuse and condemn us. Even though the Law denounces us and sin terrifies us, they still cannot plunge us into despair. For faith, which is the victor over the world (1 John 5:4), quickly declares: ‘Those things have nothing to do with me, for Christ has set me free from them.’ So it is that death, which is the most powerful and horrible thing in the world, lies conquered in our conscience through this freedom of the Spirit.
"Therefore the greatness of Christian freedom should be carefully measured and pondered. The words ‘freedom from the wrath of God, from the Law, sin, death, etc.,’ are easy to say; but to feel the greatness of this freedom and to apply its results to oneself in a struggle, in the agony of conscience, and in practice — this is more difficult than anyone can say.
"Therefore one’s spirit must be trained, so that when it becomes conscious of the accusation of the Law, the terrors of sin, the horror of death, and the wrath of God, it will banish these sorrowful scenes from its sight and will replace them with the freedom of Christ, the forgiveness of sins, righteousness, life, and the eternal mercy of God. Although the consciousness of these opponents may be powerful, one must be sure that it will not last long. As the Prophet says, ‘In overflowing wrath for a moment I hid My face from you, but with everlasting love I will have compassion on you’ (Isaiah 54:8). But this is extremely difficult to bring about. Therefore the freedom that Christ has achieved for us is easier to talk about than it is to believe. If it could be grasped in its certainty by a firm faith, no fury or terror of the world, the law, sin, death, the devil, etc., could be too great for it to swallow them up as quickly as the ocean swallows a spark. Once and for all this freedom of Christ certainly swallows up and abolishes a whole heap of evils — the Law, sin, death, the wrath of God, finally the serpent himself with his head (Gen. 3:15); and in their place it establishes righteousness, peace, life, etc. But blessed is the man who understands and believes this.
"Therefore let us learn to place a high value on this freedom of ours; not the emperor, nor an angel from heaven, but Christ, the Son of God, through whom all things were created in heaven and earth, obtained it for us by His death, to set us free, not from some physical and temporary slavery but from the spiritual and eternal slavery of those most cruel and invincible tyrants, the Law, sin, death, the devil, etc., and to reconcile us to God the Father. Now that these enemies have been defeated and now that we have been reconciled to God through the death of His Son, it is certain that we are righteous in the sight of God and that all our actions are pleasing to Him; and if there is any sin left in us, this is not imputed to us but is forgiven for the sake of Christ. Paul is speaking very precisely when he says that we should stand in the freedom for which Christ has set us free. Therefore this freedom is granted to us, not on account of the law or our righteousness but freely, on account of Christ. Paul testifies to this and demonstrates it at length throughout this Epistle; and Christ says: ‘If the Son makes you free, you will be free indeed’ (John 8:36). He alone is thrust into the middle between us and the evils that oppress us. He conquers and abolishes them, so that they cannot harm us any longer. In fact, in place of sin and death, He grants us righteousness and eternal life, and He changes slavery and the terror of the Law into the freedom of conscience and the comfort of the Gospel, which says: ‘Take heart, My son; your sins are forgiven’ (Matt. 9:2). Therefore he who believes in Christ has this freedom.
"Reason does not see how great a matter this is; but when it is seen in the Spirit, it is enormous and infinite. No one can realize with language or thought what a great gift it is to have — instead of the Law, sin, death, and a wrathful God — the forgiveness of sins, righteousness, eternal life, and a God who is permanently gracious and kind. The papists and all self-righteous people boast that they also have the forgiveness of sins, righteousness, etc.; they also lay claim to freedom. But all these things are worthless and uncertain. In temptation they vanish instantly, because they depend on human works and satisfactions, not on the Word of God and on Christ. Therefore it is impossible for any self-righteous people to know what freedom from sin, etc., really is. By contrast, our freedom has as its foundation Christ, who is the eternal High Priest, who is at the right hand of God and intercedes for us. Therefore the freedom, forgiveness of sins, righteousness, and life that we have through Him are sure, firm, and eternal, provided that we believe this. If we cling firmly to Christ by faith and stand firm in the freedom with which He has made us free, we shall have those inestimable gifts. But if we become smug and drowsy, we shall lose them." (Luther’s Works, Volume 27, CPH 1963; alt.)