by John Colqhoun
A man is to be counted a legalist or self righteous if, while he does not pretend that his obedience is perfect, he yet relies on it for a title to life. Self-righteous men have in all ages set aside as impossible to be fulfilled by them that condition of the covenant of works which God had imposed on Adam and have framed for themselves various models of that covenant, which, though they are far from being institutions of God and stand upon terms lower than perfect obedience, yet are of the nature of a covenant of works. The unbelieving Jews who sought righteousness by the works of the Law were not so very ignorant or presumptuous as to pretend to perfect obedience. Neither did those professed Christians in Galatia, who desired to be under the Law and to be justified by the Law, of whom the Apostle therefore testified that they had fallen from grace, presumed to plead that they could yield perfect obedience.
On the contrary, their public profession showed that they had some sense of their need of Christ's righteousness, but their great error was this: they did not believe that the righteousness of Jesus Christ alone was sufficient to entitle them to the justification of life. And, therefore, they depended for justification partly upon their own obedience to the moral and the ceremonial law. It was this, and not their pretensions to perfect obedience, that the Apostle had in view when he blamed them for cleaving to the law of works and for expecting justification by the works of the Law.
By relying for justification partly on their own works of obedience to the moral and ceremonial laws, they, as the apostle informed them, were fallen from grace. Christ was become of no effect to them, and they were debtors to the whole law. You see he pushes them to logical conclusion of their position, which they failed to see in their joining of works and grace. By depending for justification partly on their imperfect obedience to the law, they framed the law into a covenant of works, and such a covenant of works too as could admit of imperfect instead of perfect obedience. And by relying partly on the righteousness of Christ, they mingled the law with the gospel and works with faith in the affair of justification. Thus, they perverted both the law and the gospel. And formed for the themselves a motley covenant of works.
Excerpt from A Treatise on Law and Gospel, ed. D. Kistler (Soli Deo Gloria 1999), 18-19