Romans 5:12-21

12 Therefore, just as sin came into the world through one man, and death through sin, and so death spread to all men because all sinned— 13 for sin indeed was in the world before the law was given, but sin is not counted where there is no law. 14 Yet death reigned from Adam to Moses, even over those whose sinning was not like the transgression of Adam, who was a type of the one who was to come.

15 But the free gift is not like the trespass. For if many died through one man's trespass, much more have the grace of God and the free gift by the grace of that one man Jesus Christ abounded for many. 16 And the free gift is not like the result of that one man's sin. For the judgment following one trespass brought condemnation, but the free gift following many trespasses brought justification. 17 For if, because of one man's trespass, death reigned through that one man, much more will those who receive the abundance of grace and the free gift of righteousness reign in life through the one man Jesus Christ.

18 Therefore, as one trespass led to condemnation for all men, so one act of righteousness leads to justification and life for all men. 19 For as by the one man's disobedience the many were made sinners, so by the one man's obedience the many will be made righteous. 20 Now the law came in to increase the trespass, but where sin increased, grace abounded all the more, 21 so that, as sin reigned in death, grace also might reign through righteousness leading to eternal life through Jesus Christ our Lord.

This is a complicated passage, and I found something in one of my commentaries that has been helpful to me:

Paul paints with broad brush strokes a bird’s-eye picture of the history of redemption. His canvas is human history, and the scope is universal. We hear nothing in this paragraph of Jew and Gentile; both are subsumed under the larger category “human being.” The perspective is corporate rather than individual. All people, Paul teaches, stand in relationship to one of two men, whose actions determine the eternal destiny of all who belong to them. Either one belongs to Adam and is under sentence of death because of his sin, or disobedience, or one belongs to Christ and is assured of eternal life because of his righteous act, or obedience. The actions of Adam and Christ, then, are similar in having epochal significance. But they are not equal in power, for Christ’s act is able completely to overcome the effects of Adam’s. Anyone who “receives the gift” that God offers in Christ finds security and joy in knowing that the reign of death has been completely and finally overcome by the reign of grace, righteousness, and eternal life (vv. 17, 21). — from The Letter to the Romans, by Douglas Moo

Let’s walk through what Paul says.

From Adam, sin and death spread to all people:

12 Therefore, just as sin came into the world through one man, and death through sin, and so death spread to all men because all sinned— 13 for sin indeed was in the world before the law was given, but sin is not counted where there is no law. 14 Yet death reigned from Adam to Moses, even over those whose sinning was not like the transgression of Adam, who was a type of the one who was to come. [5:12-14]

Even before the Law was given at Sinai, there was sin. Not everyone disobeyed a direct command like Adam did, but everyone sinned, nonetheless. Adam chose sin, and unleashed death as its consequence on everyone who came after him. Jesus, in contrast, chose righteousness and unleashed life on everyone who now believes in Him. But it would be a mistake to set up Adam and Jesus as equal and opposites, yin and yang—the obedient choice Jesus made to die for rebellious humanity is much more powerful and has much greater consequences than the sinful choice that Adam made:

15 But the free gift is not like the trespass. For if many died through one man's trespass, much more have the grace of God and the free gift by the grace of that one man Jesus Christ abounded for many. 16 And the free gift is not like the result of that one man's sin. For the judgment following one trespass brought condemnation, but the free gift following many trespasses brought justification. 17 For if, because of one man's trespass, death reigned through that one man, much more will those who receive the abundance of grace and the free gift of righteousness reign in life through the one man Jesus Christ. [5:15-17]

The results of Jesus’s choice overcome the results of Adam’s choice. (Note that little phrase that those who are in Christ will “reign in life” (v. 17). This will be a key point later in Romans 8—that one of the results of salvation is that God’s people will take their place and reign over the new creation.)

18 Therefore, as one trespass led to condemnation for all men, so one act of righteousness leads to justification and life for all men. 19 For as by the one man's disobedience the many were made sinners, so by the one man's obedience the many will be made righteous. 20 Now the law came in to increase the trespass, but where sin increased, grace abounded all the more, 21 so that, as sin reigned in death, grace also might reign through righteousness leading to eternal life through Jesus Christ our Lord. [5:18-21]

The Law showed that even Israel was sinful, but Jesus—the obedient Israelite—died on behalf of sinners, proving that God’s grace is greater than any sin. Sin had its time, but the grace of God has triumphed over it, through Jesus Christ.

The result: all who trust in Jesus are righteous and have eternal life, since death no longer has power over them.