When I prayed the words “In Thy righteousness deliver me,” I thought: “O no, dear Lord God! Not in Thy righteousness in the Latin or philosophical manner of speaking but in Thy mercy!” And here, it is true, all the fathers, Augustine, and Ambrose, had idle dreams and dashed against this stumbling block, so to speak, as Ps. 25:10 states: “All the paths of the Lord are steadfast love and faithfulness.” Here they explained the paths of the Lord actively and said that God judges the devil, together with the ungodly and those who are damned, by means of His truth, but the saints by means of His mercy. But in this way the meaning of the psalm is completely obscured. Nor did they understand anything, because they did not correctly grasp the construction of the genitive. For the psalm is speaking of the ways of the Lord, of the works of the Lord which He works in us, of the faith in the Lord by which He saves us, so that all the ways of the Lord are meant. What our Lord God does with us is all grace and mercy.
Luther’s works, vol. 7: Lectures on Genesis: Chapters 38-44 p 252-253