13. But the doers of the Law will be justified. This passage is interpreted in a twofold way by blessed Augustine in chapter 26 of On the Spirit and the Letter. First in this way:The doers of the Law will be justified means that through justification they will become, will be made, what they were not before, doers. Second, and in a better way, will be justified means that they will be looked upon and thought of as righteous, as stated in the gloss. It is sufficiently clear from the preceding (the period 13), “for not the hearers of the Law are righteous before God,” that, if you should ask who else is righteous before God except the hearers, the answer would be: “The doers will be righteous, that is, they will be justified and looked upon as righteous.” Thus Ps. 143:2 says, “for no man living is righteous before Thee,” that is, he is not looked upon as righteous. And below, in Rom. 3:20, we read: “No human being will be justified in his sight by works of the law.” And again in Luke 10:29: “And he, desiring to justify himself” (that is, he wanted to declare or to state that he was righteous, and he wanted to absolve himself of sin, as though he did not know who was his neighbor whom he was commanded to love), and similarly in many other places.

—Martin Luther, Luther’s Works, 25.184–85.