Christ is not Moses, not a taskmaster or a lawgiver; He is the Dispenser of grace, the Savior, and the Pitier. In other words, He is nothing but sheer, infinite mercy, which gives and is given. Then you will depict Christ correctly. If you let Him be depicted to you any other way, you will soon be overthrown in the hour of temptation. The highest art among Christians is to be able to define Christ this way; it is also the most difficult of arts. For it is very hard for me, even in the great light of the Gospel and after my extensive experience and practice in this study, to define Christ as Paul does here. That is how much this teaching and noxious idea of Christ as the lawgiver has penetrated into my bones like oil. On this score you younger men are much more fortunate than we older ones. You have not been imbued with these noxious ideas with which I was imbued from boyhood, so that even at the mention of the name of Christ I would be terrified and grow pale, because I was persuaded that He was a judge. Therefore I have to make a double effort: first, to unlearn, condemn, and resist this ingrown opinion of Christ as a lawgiver and a judge, which constantly returns and drags me back; secondly, to acquire a new idea, namely, trust in Christ as the Justifier and the Savior. If you are willing, you can have much less difficulty learning to know Christ purely. Therefore if any sadness or tribulation afflicts one’s heart, this should not be ascribed to Christ, even though it may come under the name of Christ, but to the devil, who makes a practice of coming under the name of Christ and of disguising himself as an angel of light (2 Corinthians 11:14).
Therefore let us learn to distinguish carefully between Christ and a lawgiver, not only in word but also in fact and in practice. Then, when the devil comes, disguised as Christ and harassing us under His name, we will know that he is not Christ, but that he is really the devil. For Christ is the joy and sweetness of a trembling and troubled heart. We have this on the authority of Paul, who adorns Him with the sweetest of titles here, calling Him the One “who loved me and gave Himself for me.” Therefore Christ is the Lover of those who are in anguish, sin, and death, and the kind of Lover who gives Himself for us and becomes our High Priest, that is, the One who interposes Himself as the Mediator between God and us miserable sinners. I ask you what could be said that would be more joyful and happy than this? If all this is true—and it must be true, or otherwise the whole Gospel is false—then surely we are not justified by the righteousness of the Law, much less by our own righteousness.
Therefore read these words [in Galatians 2:20] “me” and “for me” with great emphasis, and accustom yourself to accepting this “me” with a sure faith and applying it to yourself. Do not doubt that you belong to the number of those who speak this “me.” Christ did not love only Peter and Paul and give Himself for them, but the same grace belongs and comes to us as to them; therefore we are included in this “me.” For just as we cannot deny that we are all sinners, and just as we are obliged to say that through his sin Adam destroyed us and made us enemies of God who are liable to God’s wrath and judgment and worthy of eternal death—for all terrified hearts feel and confess this, in fact, more than is proper—so we cannot deny that Christ died for our sins in order that we might be justified. For He did not die to make the righteous righteous; He died to make sinners into righteous men, the friends and sons of God, and heirs of all heavenly gifts. Therefore since I feel and confess that I am a sinner on account of the transgression of Adam, why should I not say that I am righteous on account of the righteousness of Christ, especially when I hear that He loved me and gave Himself for me? Paul believed this most firmly, and therefore he speaks with such πληροφορία [fullness of wisdom].
Luther’s Works 26:178-179