The Institutes of the Christian Religion (best navigation w/Direct Verse Jump)

by John Calvin

I admit, indeed, that if the Scripture taught nothing else on the subject than that the Law is a rule of life by which we ought to regulate our pursuits, I should at once assent to their opinion; but since it carefully and clearly explains that the use of the Law is manifold, the proper course is to learn from that explanation what the power of the Law is in man.

For if we manifest becoming reverence only when we prefer his will to our own, it follows, that the only legitimate service to him is the practice of justice, purity, and holiness. Nor can we plead as an excuse, that we want the power, and, like debtors, whose means are exhausted, are unable to pay. We cannot be permitted to measure the glory of God by our ability; whatever we may be, he ever remains like himself, the friend of righteousness, the enemy of unrighteousness, and whatever his demands from us may be, as he can only require what is right, we are necessarily under a natural obligation to obey. Our inability to do so is our own fault. If lust, in which sin has its dominion, so enthrals us, that we are not free to obey our Father, there is no ground for pleading necessity as a defence, since this evil necessity is within, and must be imputed to ourselves.

If he has not the power of subduing his passion, let him understand that the Lord has made it obligatory on him to marry.