An excerpt from Luther’s “Tower Experience”, which Luther himself dates as 1519, almost two years after his posting of the 95 Theses:

“I meditated night and day on those words until at last, by the mercy of God, I paid attention to their context: "The justice of God is revealed in it, as it is written: 'The just person lives by faith.'" I began to understand that in this verse the justice of God is that by which the just person lives by a gift of God, that is by faith. I began to understand that this verse means that the justice of God is revealed through the Gospel, but it is a passive justice, i.e. that by which the merciful God justifies us by faith, as it is written: "The just person lives by faith." All at once I felt that I had been born again and entered into paradise itself through open gates. Immediately I saw the whole of Scripture in a different light. I ran through the Scriptures from memory and found that other terms had analogous meanings, e.g., the work of God, that is, what God works in us; the power of God, by which he makes us powerful; the wisdom of God, by which he makes us wise; the strength of God, the salvation of God, the glory of God.

I exalted this sweetest word of mine, "the justice of God," with as much love as before I had hated it with hate. This phrase of Paul was for me the very gate of paradise. Afterward I read Augustine's "On the Spirit and the Letter," in which I found what I had not dared hope for. I discovered that he too interpreted "the justice of God" in a similar way, namely, as that with which God clothes us when he justifies us. Although Augustine had said it imperfectly and did not explain in detail how God imputes justice to us, still it pleased me that he taught the justice of God by which we are justified.”

(From the Preface to Luther’s Latin Works, taken from http://www.iclnet.org/pub/resources/text/wittenberg/luther/tower.txt the Project Wittenberg web site, thanks to the Reverend Robert Smith)

Image: By Marcus Singer (shifted & brightened by Rabanus Flavus) - File:Lutherhaus.jpg, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=49200465