Luther’s lectures on Galatians represent some of his clearest thought on what the Gospel is. As is a trademark of Luther, he notes at the beginning of his comments that if the doctrine of justification by faith “is lost and perishes, the whole knowledge of truth, life, and salvation is lost and perishes at the same time.” In thinking through this doctrine, Luther makes the crucial distinction between active and passive righteousness. Passive righteousness is the righteousness which saves, that is, the righteousness one receives from Christ completely outside of one’s works and which corresponds to the true Gospel and the heavenly world. Regarding passive righteousness, the Christian does nothing, but “receive and permit someone else to work in us, namely, God.” This passive righteousness stands over against what Luther calls active righteousness, or that righteousness which refers to a person’s “works, our worthiness, and the Law,” and which corresponds to the earthly world and is itself a false gospel. Practically, the difference between the two is massive, for gazing upon our active righteousness yields despair while gazing upon Christ and our passive righteousness which we receive from Him yields peace and relief from this despair. Truly, recognizing the related distinction between Law and Gospel is what makes one a “real theologian.”
Commenting on Gal. 1:3, Luther notes that Christian theology does not present God in abstraction, but in Christ, born in a manger. Thus, it is critical for the Christian to keep Christ’s mediation ever before them, for how else might they be justified and atoned for? Of course, this Christ must be Himself true God, for He grants us things which only God can grant. If Christ is not fully God, then it is difficult to see how He can forgive sins or defeat death and Satan.
What is more, as Luther meditates further on the person of Christ in Galatians, he notes that Christ is always the actor in Paul’s eyes, for He is the one who gives Himself for our sins. Indeed, Christ is the one who must do the giving, and He must do it as true God, because man’s sin is so great that it requires nothing less than the Son of God, to give Himself for it. That said, Luther is not content to leave a hypothetical atonement in the annals of theological conversation. He makes clear that when Paul says that He gave Himself for our sins, we must appropriate that pronoun as our own, for you must “believe from your heart that Christ was given for your many great sins” and for the sins of the whole world. Once one understands the gravity of this sin, then, it is even more clear that works cannot remove them, but only Christ can. Thus, “Christ is not a lawgiver; He is a Propitiator and a Savior.” This truth must especially be kept in mind on one’s deathbed, wherein the devil reminds the Christian most forcefully of all his past sins, and it is when the Christian is at his weakest. For Luther, the doctrine of justification and the person of Christ are not simply ethereal matters to be batted about in the ivory tower of theological academia. Rather, they're points at which the Christian faith speaks to individuals, providing them great comfort and assurance that God does indeed love them.