John Colquhoun (1748-1827) was a Scottish minister deeply influenced by the writings of Thomas Boston and the other "Marrow men" who had defended Edward Fisher's Marrow of Modern Divinity (1645) in the 1720's when the moderates in power in the Church of Scotland condemned the book as antinomian. "In advising the many students of divinity who frequented [Colquhoun's] ministry, he declined to recommend The Marrow of Modern Divinity, as the General Assembly had condemned it. But Boston's notes to the Marrow were not so condemned, and these he warmly recommended" (!) (Dictionary of Scottish Church History and Theology, ed. Nigel M. de S. Cameron, [T&T Clark/IVP, 1993], 196).
Colquhoun's approach to the Law, as you would expect, is very similar to that of Fisher and Boston, but even clearer and more logically organized. The Marrow is somewhat irritating due to the dialogue format, as well as the lengthy annotations by Boston. Colquhoun is more straightforward, and very readable.
Let me give you a sampling of this delightful work:
"The violated covenant of works, as I observed above, was not, and could not be, made or renewed with the Israelites at Sinai; for it was a broken covenant, and besides, it was a covenant between God and man as friends, whereas now man has become the enemy of God. But though it was not renewed with them, yet it was, on that solemn occasion, repeated and displayed to them. It was not proposed to them in order that they might consent, by their own works, to fulfill the condition of it; but it was displayed before them in subservience to the covenant of grace that they might see how impossible it was for them as condemned sinners to perform that perfect obedience which is the immutable condition of life in it ... God therefore displayed on Mount Sinai the law of the Ten Commandments as a covenant of works in subservience to the covenant of grace ... that by means of it, finding themselves utterly destitute of perfect righteousness, they might be impelled to take hold of the covenant of grace in which the perfect righteousness of the second Adam is provided and exhibited for the justification of all who believe" (pp. 55-56).
Colquhoun's exegesis of Romans 3:31: "The law received a complete answer to all its high demands by the unsinning obedience and satisfactory death of the Lord Jesus, the Surety of elect sinners. We are thereby instructed that He came into the world 'not to destroy, but to fulfill the law' (Matthew 5:17), and that He 'is the end of the law for righteousness to everyone who believes' (Romans 10:4). According to the doctrine of faith, the law as a covenant receives from our divine Surety all the obedience and satisfaction which it can demand. He, in the room, and as the representative of an elect world, fulfilled all the righteousness of it (Matthew 3:15). He yielded to it perfect holiness of human nature, perfect obedience of life, and complete satisfaction for sin; and from His divine nature, united to the human in His infinitely glorious person, His whole righteousness has derived such infinite value as to be strictly meritorious of eternal life for His spiritual seed. According to that doctrine, the law in its federal form is far more honored by the righteousness of the second Adam than it was dishonored by the disobedience of the first ... Now by this consummate, transcendently-glorious righteousness which is revealed in the gospel, the sovereign authority and high obligation of the law are most illustriously displayed and most firmly established" (pp. 179-80).
"Thus it is plain that true believers are dead to the commanding, promising, condemning, and irritating power of the law as a covenant of works" (p. 215).
"It is the inestimable privilege, as well as the indispensable duty, of all who have believed through grace to be 'dead to the law' as a covenant of works. To be dead to its relatively, or with respect to their state, is their exalted privilege; and to become dead to it really, in the disposition of their minds, is their bound duty" (p. 215).
"As the believer's living unto God, according to the law as a rule of life in the hand of the Mediator, is the necessary consequence or fruit of his having become dead to the law as a covenant of works, so his being dead to the law is necessary to his living unto God; so absolutely necessary that were he not dead to the law as a covenant, it would be utterly impossible for him to live unto God in conformity to the law as a rule" (pp. 236-7).
"This law issues to true Christians from Christ, the glorious Mediator of the New Covenant, and from God their Creator, Proprietor, Benefactor, and covenant God. It proceeds immediately from Jesus Christ, the blessed Mediator between God and men. It is taken in under the covenant of grace, and, in the hand of Christ, the Mediator of that covenant, it is given to all who believe in Him, and who are justified by faith, as the only rule of their obedience. The Apostle Paul accordingly calls it 'the law of Christ' (Galatians 6:2).... Were believers to keep the moral law only as the law of nature, and without any relation to the Mediator, their obedience would be but natural religion; were they to obey it merely as a covenant of works their obedience would be but legal righteousness; but when they obey it in its relation to Christ and the covenant of grace, their conformity of heart and life to it is true holiness, acceptable to God by Jesus Christ (1 Peter 2:5)" (pp. 26-27, 30).
"The Lord Jesus, therefore, instead of dissolving or in the smallest degree weakening the moral law, greatly strengthens the original obligation of it (Confession of Faith XIX:V). Indeed, it is only to God as in Christ, only according to the law as in the hand of Christ, and only by a real believer in Christ that the smallest acceptable obedience can be performed" (p. 134).
1. The ten commandments were given as a republication of the broken covenant of works to Israel, not as a means of justification, but in subservience to the covenant of grace as a disciplinarian to lead us to Christ.
2. As such the law given to Israel could not produce sanctification but only stirred up sin and made it increase, resulting in even greater spiritual bondage.
3. The believer has been delivered from the moral law as a covenant of works by union with Christ in his meritorious obedience and satisfactory death, by which he undertook and satisfied the claims of the broken covenant of works for us as the second Adam.
4. The believer is dead to the law and is now bound to Christ, or married to another, in order to bring forth fruit unto God.
5. The believer's ethical obligation is now to the law of Christ, which has the same content as the moral law, but taken up and renewed in Christ, and so the moral law comes to us in new covenant form grounded in union with Christ.
John Colquhoun, A Treatise on the Law and the Gospel (Morgan, PA: Soli Deo Gloria, 1999, originally 1819).