These are great words from John Colquhoun (d. 1827) in A Treatise on the Law and the Gospel.
“In the affair of justification, the law as a covenant of works is not only to be distinguished, but to be separated from the gospel. When a true believer is at any time in doubt of his justification and title to eternal life, he ought to set the law as a covenant, and the works of that law, entirely aside, and to rely anew, for all his title to life eternal, on the spotless righteousness of the second Adam offered to him in the gospel.”
“He ought in that case to contemplate only the free and super-abounding grace of the gospel, and to embrace, by the renewed exercise of an appropriating faith, the gracious offers and promises of it. He should exclude from his view the law and all legal righteousness, and, relying only on the righteousness of Christ revealed in the gospel, he should trust that this glorious, this consummate righteousness alone gives him a complete title to justification and eternal life.”
“As it is not by the law, nor the works of the law, but by means of faith only, applying the righteousness brought near in the gospel, that a man is justified before God; so in the business of his justification he must set aside all works of the law and depend wholly on the righteousness and grace of the great Redeemer. While in the business of sanctification the law as a rule is to be connected with the gospel, in that of justification the law as a covenant is always to be separated from it” (p. 157).