Now take both Laws, the Ceremonial Law and the Moral Law or the Decalog. Imagine that by the merit of congruity you have made so much progress that the Spirit has been granted to you and that you have love. Of course, all this would be a monstrosity and cannot be found anywhere in the nature of things. But imagine, I say, that, by doing what lies within you, you acquire grace, are righteous, and have the Spirit. On what basis? On the basis of the merit of congruity? Then you do not need Christ, but He has become useless to you and died to no purpose.
Martin Luther, Luther’s Works, Vol. 26: Lectures on Galatians, 1535, Chapters 1-4, ed. Jaroslav Jan Pelikan, Hilton C. Oswald, and Helmut T. Lehmann, vol. 26 (Saint Louis: Concordia Publishing House, 1999), 181.