the Justice of God by james d.g. dunn
Here is a collection of my three posts summarizing this book

Intro
In this short book james dunn briefly outlines how part of our understanding of "justification by faith" was obscured during the Reformation, becoming to individualistic and overly focused on legal aspects, rather than communally and relationally focused. He trace some missteps of the Luther’s recovery of the doctrine of "justification by faith" and then walks us back into the more relational world of Paul’s original formulation, and then back into the OT expression of justice/justification/righteousness

Martin Luther and the Individual Conscience

The first chapter explores the story of Luther's dramatic recovery of this very important doctrine, and two of its wrong turns.

The Recovery
While an Augustinian monk, situated within a Roman Catholicism of indulgences and purgatory, Luther's conscience ached with guilt over his sin before "the justice of God," i.e. that God punishes all unrighteousness. God, for Luther, was to be feared, not loved. But under a prolonged reading of Roman, grappling with the strange manner in which Paul refer to “the justice of God” as a means of salvation, Luther saw the light. It’s not that God is merely a "just God," but He is also the "justifying God." The decisive (f)act of God is not that he is just (condemning the wicked), but that He is the one who justifies (acquits the wicked). And much more could be said about the positive aspects of this recovery...

The Wrong Turns
But Dunn then points out two problems with how Luther explain Paul's doctrine of justification. First, Luther assumed that Paul had gone through the same agonies of conscience and guilt over sin before a blameless and just God, that Luther had been through. He assumed that Paul had been striving to know and please God through 'works of the Law' before making the discovery that he is "justified by faith" in Christ. But the problem with this is that Paul nowhere sounds like had a guilty conscience before God. Instead he says he was blameless in regards to righteousness within the law (Phil. 3:6). So, Luther was projecting his situation back into Paul’s, thereby creating distortion is his understanding of the doctrine.

A second distortion was cause by another retojection made by Luther. Quite naturally, he assumed that ancient Judaism must have been similar to mediaeval Catholicism by focusing on "justification by merit" or "by works." For Luther, Judaism was a legalistic religion of human striving. And this view has been perpetuated to this day in most Protestant traditions. But, again, this is not really the case, but a caricature. The Judaism of Paul's day, and the one we can read about in the OT. Yes there is the Law, but God grace is choosing Israel, dwelling with Israel in the midst of their sin (allowing for repentance and forgiveness), and the continual prophetic recalling of God’s righteous act to an unworthy nation should reveal the caricature of Judaism as merely a religion of works righteousness.

Justice for Gentiles: Paul and Justification by Faith

In the second chapter Dunn outlines the contours of Jewish faith at the time of Christ and what exactly Paul was converted to (or rather, commissioned to), shedding light on his resultant doctrine of "justification by faith."

the Shape of Judaism
At the time of Paul, two tenets of Judaism were taken for granted: 1) God is one; and 2) God had chosen Israel to be His special people. The second aspect, the theology of election, meant that Israel was different than the other nation, and had to sustain that distinctiveness at all costs. And this distinctiveness as marked out through the Torah, or Law. The foundation of this for Israel is not that they had to earn God’s favor and stay in His good graces, but that they were chosen to be God’s people and instrument among the nations. This election of Israel through the giving of the Law meant that the Gentiles were extremely disadvantaged, being "outside" the Law, and therefore outside God's favor.

So, what was Paul converted from? He was converted from a 'zealous' attachment to Israel’s distinctiveness (separated from the Gentiles) and step up by the Law (as a boundary marker b/w Jew and Gentile, particularly circumcision and food laws). He was converted from a rigid nationalism which had forgotten that the election of Israel was meant for the benefit of the Gentiles also, not to their exclusion.

Commission, not Conversion
So, what was Paul converted to? A better question is to ask about his commission , not his conversion. On the Damascus road Paul was commissioned to preach the Gospel to the Gentiles. And it is this commissioning that changed everything. Being confronted with the risen Lord Jesus Messiah, Paul had to come to grips with theses Christians who being so friendly to Gentile, because now he was commissioned to preach to them. As we will now see, "the Christian doctrine of justification by faith begins as Paul's protest not as an individual sinner against Jewish legalism, but as a protest on behalf of Gentiles against Jewish exclusivism" (p. 24).

the Shape of Justification
Dunn now shifts gears to see what light can be shed on the Luther's formulation of this doctrine. Justification by faith, for Paul, was not merely the conviction that sinners cannot rely on their own merit to earn God’s favor (although Paul would certainly agree with this). Rather, it is the conviction that God grace is not limited to a particular people (defined as those who follow the Law), but that God's goodness and mercy is open to all people through Faith. One of the main points (and the one forgotten by the Reformation) is that one doesn’t have to change cultures to be accepted by God (i.e. change from a Gentile into a Jew to be saved). Rather, through Christ, all are justified by faith, b/c God's grace is not locked into a certain people, but mediated through a certain person, our Lord Jesus Christ, Son of God, Messiah, Savior.

the Justice of God

The last dimension of this subject that Dunn examines is the Old Testament concept of the Justice of God. For this concept lies beneath and is assumed by Paul when he speaks of "justification by faith."

Righteousness in relationships
Righteousness is not an ideal to be grasped or approximated, but the manner of a relationship. Dunn points out that justice/righteousness in Greek and Roman thought is an ideal but which we evaluate individual to be just or righteous. Justice/righteousness is an absolute ethical norm by which we measure particular instances. "'Justice' was like a divine principle of order which had to be sustained and appeased lest disorder and anarchy prevail'(33). But in contrast to this, justice/righteousness in the OT is not an ideal for individual to strive after, but in Hebrew thought it is a concept of relation, "something one has precisely in one's relationships as a social being'(33). So, "people are righteous when they meet the claims which others have on them by virtue of their particular relationships"(33).

Concerning God, then, He is righteous toward His creation b/c He sustains it and causes it to thrive. God is righteous toward Israel b/c He sustains His people (even when the act unrighteously toward Him) and he causes Israel to thrive. Because God undertook a relationship with Israel by His own free act of Grace (the doctrine of election we talked about before), God is acting righteously when He continues that relationship, even when the people sin/rebel. According to Greek/Roman ideals of justice, God must punish sin/wickedness and should therefore cast off his rebellious people. But this has no room for forgiveness or a relationship based in Love.

Concerning Israel, they are not righteous merely by observing the Law (a works righteousness), but b/c through the Law they maintain a relationship with God, one started and renewed through God’s grace. This places justice/righteousness more in the category of God spontaneous act of Love, rather than a punitive act of judgment.

Horizontal and Vertical
While I don't have enough time to explain this more, the last section of Dunn's little book focuses on the intimate link b/w our righteous relations with each and a righteous relationship with God. The link, esp. for the major prophets, is through worship. One cannot worship God truthfully/righteously when our relationship with others are oppressive, esp. against the poor and marginalized. We cannot be righteous with God if we are perpetuating/participating in unrighteous relationships among people.

Summary
"To sum up then. The biblical understanding of justification/justice/righteousness is all of a piece...Righteousness as essentially involving relationships, arising our of relationships, expressed in relationships; and righteousness, as both horizontal and vertical, as involving responsibility to one’s neighbor as part and parcel of one’s responsibility towards God"(42).