Herman Bavinck: Law/Gospel Contrast...

“While, on the one hand, the Reformers held on to the unity of the covenant of grace in its two dispensations against the Anabaptists, on the other hand they also perceived the sharp contrast between law and gospel and thereby again restored the peculiar character of the Christian religion as a religion of grace.  Although in a broad sense the terms ‘law’ and ‘gospel’ can indeed be used to denote the old and the new dispensation of the covenant of grace, in their actual significance they definitely describe two essentially different revelations of divine will.

“Also the law is the will of God; holy, wise, good, and spiritual; giving life to those who maintain it, but because of sin it has been made powerless, it fails to justify, it only stimulates covetousness, increases sin, arouses wrath, kills, curses, and condemns.  Over against it stands the gospel of Christ, the euangellion, which contains nothing less than the fulfillment of the Old Testament promise, which comes to us from God, has Christ as its content, and conveys nothing other than grace, reconciliation, forgiveness, righteousness, peace, freedom, life, and so forth.

“In these texts law and gospel are contrasted as demand and gift, as command and promise, as sin and grace, as sickness and healing, as death and life.  Although they agree in that both have God as author, both speak of one and the same perfect righteousness, and both are addressed to human beings to bring them to eternal life, they nevertheless differ in that the law proceeds from God’s holiness, the gospel from God’s grace; the law is known from nature, the gospel only from special revelation; the law demands perfect righteousness, but the gospel grants it; the law leads people to eternal life by works, and the gospel produces good works from the riches of eternal life granted in faith; the law presently condemns people, and the gospel acquits them; the law addresses itself to all people, and the gospel only to those who live within its hearing; and so forth.”

Herman Bavinck, Reformed Dogmatics Vol. 4.
[HT: Reformed Reader]