Charles H. Spurgeon on Psalms 19:7

"The law of the Lord is perfect, converting the soul." To man fallen, the law only convinceth of sin, and bindeth over to death, it is nothing but a killing letter; but the gospel, accompanied by the power of the Spirit, bringeth life. Again, it is said, "The law of the Lord is perfect, converting the soul;" therefore it seems the law may also be a word of salvation to the creature. I answer; by the law there, is not meant only that part of the word which we call the covenant of works, but there it is put for the whole word, for the whole doctrine of the covenant of life and salvation; as Psalm 1:2: "His delight is in the law of the Lord; and in his law doth he meditate day and night." And if you take it in that stricter sense, then it converteth the soul but by accident, as it is joined with the gospel, which is the misery of life and righteousness, but in itself it is the law of sin and death. Look, as a thing taken simply, would be poison and deadly in itself, yet mixed with other wholesome medicines, it is of great use, is an excellent physical ingredient; so the law is of great use as joined with the gospel, to awaken and startle the sinner, to show him his duty, to convince him of sin and judgment; but it is the gospel properly that pulls in the heart. —Thomas Manton.