Paul mentions several important details about Jesus in these verses. First, the apostle says that what Jesus did was an expression of grace (v. 15). Paul’s way of explaining its gracious aspect includes an affirmation of the deity of Jesus. The grace is called both ‘the grace of God’ and ‘the grace of that one man Jesus Christ’. Paul is saying that Jesus is equally the source of the grace that was shown to those who had sinned in and with Adam. Although he had become a man, Jesus had not ceased to be divine.
Second, Paul states that this grace revealed in Jesus abounded towards those in Adam (vv. 15-16). In order to show how it abounded, Paul contrasted what preceded the judgement imposed on Adam and what precedes the blessing received through Jesus. What occurred before judgement was pronounced on Adam was one rebellious act whereas what occurred before the blessing was received through Jesus were many rebellious acts by those who then trusted in Jesus. This was the opposite of what would have been expected. After all, if one wrong action brought such condemnation, surely many wrong actions would result in further condemnation! But to those who had been condemned for their sin in Adam God had something different to say.
Third, the free gift that is given through grace is said to be justification, which is the opposite of condemnation (vv. 16-17). Paul uses a contrast to help his readers appreciate its amazing features. The contrast is between the effect of condemnation and the effect of righteousness: the effect of condemnation was to experience death and the effect of justification is to ‘reign in life’. Paul says that death reigns over those in Adam, that each one is its slave, under its power. In contrast, Paul then says that those in Christ reign, and this reveals the amazing consequence of justification. Those who were imprisoned under divine condemnation receive a kingdom from God. Adam had been created to rule over God’s domain on earth and share it with his descendants. He and they lost it. But in Jesus, those who by faith are justified share his inheritance.
Fourth, justification is said in verse 17 to be righteousness, which is the same as perfect obedience. Furthermore, in verse 18, the righteousness is also called ‘one act of righteousness’. Which action of Jesus, the one man, brought this about? No doubt, it would be possible to suggest particular moments, but Paul is referring to the entirety of the life of obedience that Jesus lived while on earth. He was dedicated to the service of God at every stage of his life and his dedication was always perfect. But his dedication was not only for his own benefit, as it were; it would also benefit rebels against God who believed in Jesus. The perfect One was condemned for the sins of the rebellious in order that the condemned rebels could have the same righteousness as the perfect One. No wonder Paul describes it as abounding grace.
Fifth, Paul mentions the consequence of righteousness (v. 21). Again he uses contrasts, this time contrasting sins’ increasing domain of death and grace’s domain leading to eternal life. Paul here is reminding us of the way to eternal life (which is by receiving the righteousness of Jesus) and the wealth of eternal life (which is that God will give to his people all that the eternal inheritance includes).
These five reasons help us make sense of what Jesus did for sinners. And understanding what he did should make us thankful and joyful.