"If you are a preacher of grace, then preach a true and not fictitious grace; if grace is true, you must bear a true and not fictitious sin. God does not save people who are only fictitious sinners. Be a sinner, and sin boldly, but believe and rejoice in Christ even more boldly, for he is victorious over, sin, death and the world. As long as we are here, we have to sin. This life is not the dwelling place of righteousness, but, as Peter says, we look for a new heavens and a new earth in which righteousness dwells. It is enough that by the riches of God's glory we have come to know the Lamb that takes away the sin of the world. No sin will separate us from the Lamb, even though we commit fornication and murder a thousand times a day. Do you think that the purchase price that was paid for the redemption of our sins by so great a Lamb is too small? Pray boldly - you too are a mighty sinner."
Martin Luther, Letter to Melanchthon, Luther's Works, Vol. 48, page 281
(quoted in Michael Spencer, Mere Churchianity, page 137