In theology there is a new “doing”

Thus the same epistle says of Abel that by faith he offered up a better sacrifice to God than Cain did (Heb. 11:4). If the sophists come upon this passage as it is written in Genesis (where it is simply described that both Cain and Abel offered up their gifts, and that the Lord had regard for Abel and his offering [Gen. 4:3–4]), they immediately take hold of the words “they offered gifts” and “the Lord had regard for Abel’s offering.” And they exclaim: “Here you can hear and see that God had regard for offerings; therefore works do justify!” Thus these filthy swine think that righteousness is something moral, since they look only at the mask of the work and not at the heart of the one who is doing the work. And yet in philosophy itself they are obliged to look, not upon the bare work but upon the good will of the one who does the work. But here they simply cling to the words “they offered gifts” and “the Lord had regard for offerings”; they do not see that the text in Genesis explicitly states that the Lord had regard first for Abel because his person was pleasing on account of faith, and only then for his offerings. In theology, therefore, we speak of works, sacrifices, offerings, and gifts that are faithful, that is, that are offered and performed in faith, as the Epistle to the Hebrews explains. “By faith,” it says (Heb. 11:4), “Abel offered a more acceptable sacrifice”; “by faith Enoch was taken up” (Heb. 11:5); “by faith Abraham obeyed” (Heb. 11:8). Here, then, you have a rule about how one should reply plainly to the arguments raised by our opponents about works, namely, “This or that man did this work in faith.” And thus you nullify all their arguments. From this it is evident that in theology the work does not amount to anything without faith, but that faith must precede before you can do works. For “without faith it is impossible to please God, but whoever would draw near to God must believe” (Heb. 11:6). Therefore the writer of the Epistle to the Hebrews says that the sacrifice of Abel was better because he believed. But because Cain was an ungodly man and a hypocrite, he performed a work that was moral, or rather one that was reasonable, by which he sought to please God. Therefore the work of Cain was hypocritical and faithless; in it there was no faith in grace but only a presumption about his own righteousness. And so the “doing,” the gift, and the offering of Abel are faithful; but those of Cain are faithless. Thus our opponents are forced to concede that in all the works of the saints the faith on account of which the works are pleasing is presupposed. In theology, therefore, there is a new “doing,” one that is different from moral “doing. –Martin Luther