In Romans 4:5, Paul identifies God as the one “who justifies the ungodly.” Those who read this passage as an abstract discussion of the mechanics of justification will conclude that Paul is stressing the purely passive manner in which justification is received by morally unworthy people. It does not come as a result of anything that someone does.
This is partially true. Justification is indeed a gift from God and it can’t be earned by human achievement.
But that isn’t exactly Paul’s point here.
Paul is taking a sarcastic shot at the Jews’ prejudice against non-Jews—those “ungodly” ones. He means to offend the Jewish Christians’ presumption that they have an inside track with God.
Paul intensifies his sarcasm in Rom. 5:6, where he notes that “while we were still helpless, at the right time Christ died for the ungodly.” His rhetoric demands that Jewish Christians identify themselves alongside the non-Jewish Christians as those who are “helpless” and “ungodly.”
If they refuse this self-identification, they also refuse to identify themselves with the death of Christ, putting them outside the scope of salvation.
Paul is undermining the self-righteousness of any group of people who look at themselves as in any way superior to other people before God.
The rhetorical force of Paul’s words does not necessarily have to do with the mechanics of justification the way they were developed in subsequent centuries, especially in dogmatic debates regarding the workings of salvation with reference to the individual before God.
The rhetorical force of what Paul says has to do with relativizing all the groups in Rome, unifying them as both equally unworthy and equally loved by God. Everyone must recognize their full membership in the “ungodly” group in order to be part of the “justified” group.