Previously on Paul.
The Faith of Jesus Christ
The first three chapters of Romans, especially Romans 1:18-3:20, present the human problem. God will judge both Jew and non-Jew on the basis of how they have lived in this life (Rom. 2:6). But both Jew and Gentile have done wrong, have sinned, are alienated from God. The default human situation is that both Jew and Gentile stand apart from God on a trajectory to receive God's wrathful judgement on the Day of Wrath.
Romans 3:21-4:25 lay out God's solution to this conundrum. On the one hand, God is a God of justice (Rom. 3:25-26). I personally believe he could simply pardon all humanity on his own divine authority, but such an action would leave us without a clear sense of his justice or of the serious breach of cosmic order that currently exists. But God is also a faithful, saving God. The "righteousness of God" is wrath toward those who stand apart from him (Rom. 1:18). But the righteousness of God is to act to save and make a path of reconciliation to those who will avail themselves.
The solution to the human sin problem is the "faith of Jesus Christ" (Rom. 3:22). I have a hunch that Paul intended a double entendre, a double meaning with this phrase. It could mean either "the faithfulness of Jesus Christ" or our faith in Jesus Christ. I wonder if Paul meant the Romans to hear both. The solution is the faithful obedience of Jesus to the point of death, the faithful death of Jesus through which God atones for the sins of humanity, and our trust in what God has done through Jesus.
In Romans 3:21-22, Paul says that God has now revealed his righteousness apart from the Law, namely “through faith of Jesus Christ to all who have faith.”  Almost all translations render this phrase “through faith in Jesus Christ,” but you can see that someone might very easily take it to say “through the faith of Jesus.” Many interpreters now take the expression that way.  Paul would thus be saying that God has now shown his righteousness through the faithfulness of Jesus, through Jesus' obedience unto death (cf. Phil. 2:8; Rom. 5:19). The experts are divided on the issue, and the Greek is genuinely ambiguous. 
 My translation.
 Perhaps the best known current proponent of this interpretation is Richard B. Hays. In the first volume of this series, Paul: Messenger of Grace, we mentioned Hays' The Faith of Jesus Christ as one of the many books one might read to master Paul (The Faith of Jesus Christ: The Narrative Substructure of Galatians 3:1-4:11, 2nd ed. [Grand Rapids: Eerdmans, 2002]).
 The best known proponent of the traditional reading “faith in Jesus” is James D. G. Dunn, whose rebuttal is printed at the end of the revised edition of Hays’ Faith of Jesus Christ (Faith, 249-71). The first volume of my Paul series was in part dedicated to Dunn, under whom I studied. This volume is in part dedicated to Hays.