For the Christian, therefore, endeavoring to keep the law was not to be construed as evidence of being under the law as a covenant of works. But a man under the covenant of grace should equally endeavor to keep God’s law. There is no contradiction between the grace of the gospel and the usage of the law in the life of the believer. Grace and law are complementary to each other, because it is the Spirit of Christ, given in grace, who subdues and enables man’s otherwise stubborn and rebellious will “to do that freely and cheerfully which the will of God revealed in the law requireth to be done.” (WCF 19.6, 7)

Andrew A. Woolsey, Unity and Continuity in Covenantal Thought: A Study in the Reformed Tradition to the Westminster Assembly, 89.