Romans chapter 5 verse 12 holds the key to understanding justification by faith, the declaration or imputation of God's righteousness which comes the believer by faith alone. Such a bold claim in the gospel seems strange and hard to grasp and yet it is founded on one of the the most common experiences of human existance, that of death. Just as in receiving the nature of Adam we receive with this his death and his sin, so too in receiving Christ, in being in Christ we receive a new nature and with it life and righteosness. That old nature was condemned in Adam and thus remains condemned when we receive it. The new nature is justified in Christ and remains justified when we receive it! In Adams fall we sinned all.
Dr J Stewart Gillespie
Bible Teaching From Romans