The duty of the law is impossible. The apostle tells us ‘what the law could not do, in that it was weak through the weakness of our flesh.’ It could not justify us before God, it could not furnish us with any answer to his demands, when he shall all us to an account. Man is mightily addicted to the legal covenant, therefore it is one part of a gospel minister’s work to represent the impossibility of ever obtaining grace or life by that covenant. Man would stick to the law as long as he can, and will patch up a sorry righteousness of his own, some few superficial things. He makes a short exposition of the law, that he may cherish a large opinion of his own righteousness; and curtails the law of God, that the ell may be no longer than the cloth, and brings it down to a poor contemptible thing, requiring a few external superficial duties of men.
Thomas Manton, “Sermon on Psalm 32:1-2”, The Complete Works of Thomas Manton, vol II, Homewood, AL: Solid Ground Christian Books, 2008, 182.