The teaching of justification by faith alone stands as one of the five Solas of the Reformation. Sola Fide served as the battle cry for the Reformers who declared that a person is saved or justified by faith alone apart from the works of the law. It was Martin Luther who rediscovered this biblical doctrine during his tenure as a lecturer in biblical studies at the University of Wittenberg. As he studied, he became convinced that the primary source of Christian theology was not the papal traditions but rather the Bible itself, especially interpreted through the lens of Augustine of Hippo. This discovery eventually lead Luther to rebuild the church from the ground up as in an effort to be faithful to the command of Scripture that the believer is simultaneously a righteous person and a sinner (simul justus et peccator). Thus, the foundation laid by Luther may well be the reason he is attributed with the statement, “Justification is the article by which the church stands and falls.”
Martin Luther’s understanding of δικαιοσύνη θεοῦ changed the course of church history, but what preceded the Reformation was a distinctly different understanding of the meaning “righteousness of God.” Luther’s understanding of δικαιοσύνη θεοῦ served as the catalyst that launched the Reformation. In essence, Luther sought to understand how one obtained favor before God. In other words, Luther wanted to know how humanity entered into a relationship with God, one that would save from damnation, death, and hell. Of course, the medieval and Catholic answer to this was the sacraments and the need for intermediaries, such as Mary and the saints. Nevertheless, Luther still wrestled with this as the basis, and it was primarily from how Paul used the phrase δικαιοσύνη θεοῦ.
Luther’s vision of God served as the foundation for what he thought about everything else, especially with the notion of sin and the Law. He knew that people stood condemned before a holy God, and he rejected the notion that people could earn their righteousness. Yet upon his reading of Romans, Luther struggled still with δικαιοσύνη θεοῦ.
I had conceived a burning desire to understand what Paul meant in his Letter to the Romans, but thus far there had stood in my way, not the cold blood around my heart but that one word which is in chapter one: “The justice of God is revealed in it.” I hated that word, “justice of God,” which by the use and custom of all my teachers, I had been taught to understand philosophically as referring to formal or active justice, as they call it, i.e., that justice by which God is just and by which he punishes sinners and the unjust.
It was not until after Luther meditated upon those words that he fully understood what they meant in their proper context.
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 one 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.
From these quotes, it appears that Luther’s understanding of δικαιοσύνη θεοῦ is primarily related to the gift of righteousness that is imputed unto the believer. Thus, Luther’s outlook upon God had changed and he no longer hated God as he previously did. The righteousness obtained by the believer is entirely passive and the believer does nothing to obtain it. “But this righteousness is heavenly and passive. We do not have it of ourselves; we receive it from heaven.”
 Alister McGrath, Christianity’s Dangerous Idea: The Protestant Revolution-A History from the Sixteenth Century to the Twenty-First (New York: Harper Collins, 2007), 42.
 Balthasar Meisner attested it was a proverb of Luther. “That saying of Luther, which has often been cited, is most true: ‘Justification is the article by which the church stands and falls.” Philip J. Secker, The Lutheran Confessions: Selected Writings of Arthur Carl Piepkorn, Volume Two (Mansfield, CT: CEC Press, 2007), 260 nc. The closest example found is, “Because if this article [of justification] stands, the church stands; if this article collapses, the church collapses.” Alister E. McGrath, Iustitia Dei: A History of the Christian Doctrine of Justification; Vol. 2 From the 1500s to the Present Day. Cambridge: Cambridge University Press, 1986), 20; cited from Thomas R. Schreiner, Faith Alone: The Doctrine of Justification (Crossway: Wheaton, 2015), 40 n20.
 Thomas R. Schreiner, Faith Alone: The Doctrine of Justification (Crossway: Wheaton, 2015), 40.
 McGrath helpfully summarizes Luther’s position. “Works are a condition, but not a cause of salvation.” McGrath, Iustitia Dei, 214.
 Martin Luther, “Preface to the Complete Edition of Luther’s Latin Works,” n.p. [cited 13 June 2016]. Online: http://www.iclnet.org/pub/resources/text/wittenberg/luther/preflat-eng.txt. Emphasis added.
 Timothy George notes that Luther rejected the notion that δικαιοσύνη θεοῦ is imparted unto the believer. “Luther abandoned the medical imagery of impartation/infusion in favor of the forensic language of imputation.” Timothy George, Theology of the Reformers (Nashville: B&H Academic, 2013), 70. George’s discussion of Luther’s formulation of this understanding of justification on pp 70–71 is likewise helpful.
 “The outworking of this, then, is that God’s justice is given to men, and this is how they are justified. Luther took his interpretation of the righteousness of God to be a powerful tool in understanding Paul’s letter to the Romans, but it also influenced him, not to mention innumerable theologians since the Reformation, to understand much, if not all, of Scripture in a completely different way.” Nicholas Dodson, “Paul’s Use of ΔΙΚΑΙΟΣΥΝΗ ΘΕΟΥ and the New Perspective Interpretation” JMAT 19 (2015): 136–137.
 Martin Luther, Lectures on Galatians 1535: Galatians 1–4 (St. Louis: Concordia, 1964), 8.