As Paul also writes in 1 Corinthians 15:56-57, The sting of death is sin, and the power of sin is the law. But thanks be to God, who gives us the victory through our Lord Jesus Christ. And therefore, ...sin will have no dominion over you, since you are not under law [as a covenant] but under grace [as a covenant] (Romans 6:14). The reign of sin exists only where the law as a broken covenant exists. In Christ that law covenant has been satisfied and thus the curse removed and righteousness won for the elect, rendering sin impotent as a ruler in that it no longer carries with it the condemnation of the law and the penalty of death (Romans 8:1-2). Whereas sin reigned over sinners condemned under the law, Christ now reigns over sinners justified under grace. Thanks be to God indeed!
"2d, Jesus saves his people from the dominion or reigning power of sin." He that committeth sin, is the servant of sin." God had told the first Adam, as the federal head of all his natural posterity, that in the day he ate of the forbidden fruit, he should surely die. No sooner did he eat of it than he was punished with the loss of spiritual life; or, in other words, with the loss of the original righteousness of his nature, in which the spiritual life of the soul consists. Now, the corruption of the whole nature, or the dominion of sin in the soul follows as naturally, upon the want of original righteousness, as darkness follows the setting of the sun. Those, therefore, whom God hath appointed to obtain salvation, as they were involved in the guilt of Adam's first transgression as well as others, and consequently born under the condemning power of the law, which, in this sense, is the strength of sin; so they are all born destitute of original righteousness, and subject to the dominion of sin. The condemning power of the law as a covenant, so long as they continue under it, detains them as prisoners, under the reigning power of depravity. No sooner, however, does the Lord Jesus, whose office it is to say to such prisoners, "Go forth!", come and admit them to communion with himself, in his surety-righteousness, than they are delivered from the condemning power of the law, and consequently, from the reigning power of sin. This infinitely glorious righteousness [i.e. imputed righteousness], as it entitles them to the sanctifying influences of the Holy Spirit, so it removes the curse of the law, which formerly stood in the way of those influences, and obstructed their entrance into the soul. Hence are these words of the apostle Paul: "Sin shall not have dominion over you; for ye are not under the law, but under grace," Rom. vi. 14.
"If believers would make more use of the righteousness of the incarnate Redeemer in their approaches to God than they do, they should find that sin would not prevail against them so much as it does."
- John Colquhoun. Sermon XIV, Salvation from Sin.(Bracketed comments and emphasis added)