The office and use of the moral law.

John Calvin has written:

“That the whole matter may be made clearer, let us take a succinct view of the office and use of the Moral Law. Now this office and use seems to me to consist of three parts. First, by exhibiting the righteousness of God,—in other words, the righteousness which alone is acceptable to God,—it admonishes every one of his own unrighteousness, certiorates, convicts, and finally condemns him. This is necessary, in order that man, who is blind and intoxicated with self-love, may be brought at once to know and to confess his weakness and impurity. For until his vanity is made perfectly manifest, he is puffed up with infatuated confidence in his own powers, and never can be brought to feel their feebleness so long as he measures them by a standard of his own choice. So soon, however, as he begins to compare them with the requirements of the Law, he has something to tame his presumption. How high soever his opinion of his own powers may be, he immediately feels that they pant under the heavy load, then totter and stumble, and finally fall and give way. He, then, who is schooled by the Law, lays aside the arrogance which formerly blinded him. In like manner must he be cured of pride, the other disease under which we have said that he labours. So long as he is permitted to appeal to his own judgement, he substitutes a hypocritical for a real righteousness, and, contented with this, sets up certain factitious observances in opposition to the grace of God. But after he is forced to weigh his conduct in the balance of the Law, renouncing all dependence on this fancied righteousness, he sees that he is at an infinite distance from holiness, and, on the other hand, that he teems with innumerable vices of which he formerly seemed free. The recesses in which concupiscence lies hid are so deep and tortuous that they easily elude our view; and hence the Apostle had good reason for saying, “I had not known lust, except the law had said, Thou shalt not covet.” For, if it be not brought forth from its lurking-places, it miserably destroys in secret before its fatal sting is discerned.”

(Calvin, John. Institutes of the Christian Religion, Grand Rapids, MI: Wm. B. Eerdmans Publishing, 1998, p. 304-305.)