Most commentators agree that verses 16 and 17 constitute the theme of the letter.

Verse 17 tells us that the gospel reveals ″the righteousness of God″. Righteousness is normally used to speak of a relationship that is right. However, Paul may also be speaking here of the righteous character of God-that God is just. When the gospel is preached, it reveals God's justice and yet, at the same time, it also reveals God's mercy. It shows how sinful humans can have a right relationship with Him.

Paul makes it clear that this relationship is by faith, not earned. He quotes Habakkuk 2:4, that those who are righteous live simply by their faithfulness-by trusting God.

Martin Luther, the 16th-century Augustinian monk, was haunted by God's righteousness and by his own sin. He tried every means the church offered in his quest for peace with God. ″I greatly longed to understand Romans and nothing stood in the way but that one expression, ‘the justice of God', because I took it to mean that justice whereby God is just and deals justly in punishing the unjust. My situation was that, although an impeccable monk, I stood before God as a sinner troubled in conscience . . . Then I grasped that the justice of God is that righteousness by which, through grace and sheer mercy, God justifies us through faith. Then I felt myself to be reborn and to have gone through open doors into paradise.″

Luther went on to lecture on Romans and to write a commentary on it. It was on hearing a public reading of the introduction to Luther‘s commentary that John Wesley, founder of the Methodist movement, felt his heart ″strangely warmed″ and was converted. Here is a truth that has changed the course of history, a righteousness coming to us by grace, through faith, based on the finished work of Jesus Christ. This is what the gospel and ″the righteousness of God″ is all about.