Luther: Be a sinner, and let your sins be strong

The following is from the web page Luther, Exposing the Myth, under the heading "On Sin":

"Be a sinner, and let your sins be strong, but let your trust in Christ be stronger, and rejoice in Christ who is the victor over sin, death, and the world. We will commit sins while we are here, for this life is not a place where justice resides... No sin can separate us from Him, even if we were to kill or commit adultery thousands of times each day" ['Let Your Sins Be Strong, from 'The Wittenberg Project;' 'The Wartburg Segment', translated by Erika Flores, from Dr. Martin Luther's Saemmtliche Schriften, Letter No. 99, 1 Aug. 1521. - Cf. Also Denifle’s Luther et Lutheranisme, Etude Faite d’apres les sources. Translation by J. Paquier (Paris, A. Picard, 1912-13), VOl. II, pg. 404].

Luther Exposing the Myth says their stated purpose is to show that "from Luther’s own words we shall see him for what he really was, that is a rebellious apostate, who abandoned the faith and led many into apostasy from God under the guise of “reformation” in order to follow his perverse inclinations." With this quote, they attempt to show Luther promoted sin.

Documentation
Luther, Exposing the Myth cites multiple references:

'Let Your Sins Be Strong, from 'The Wittenberg Project;' 'The Wartburg Segment', translated by Erika Flores, from Dr. Martin Luther's Saemmtliche Schriften, Letter No. 99, 1 Aug. 1521. - Cf. Also Denifle’s Luther et Lutheranisme, Etude Faite d’apres les sources. Translation by J. Paquier (Paris, A. Picard, 1912-13), VOl. II, pg. 404.

The "Wittenberg Project" refers to Project Wittenberg, an on-line source for Luther-related documents. " 'The Wartburg Segment', translated by Erika Flores, from Dr. Martin Luther's Saemmtliche Schriften, Letter No. 99, 1 Aug. 1521" refers to this web page from Project Wittenberg. If one looks at the page carefully, it isn't "The Wartburg Segment" but rather It's a letter Luther composed "From the Wartburg" and only a segment is translated.

"Denifle’s Luther et Lutheranisme, Etude Faite d’apres les sources. Translation by J. Paquier (Paris, A. Picard, 1912-13), VOl. II, pg. 404" refers to Heinrich Denifle's second volume on Luther (in French, not available in English). Page 404 can be found here. and there is nothing remotely similar to the quote on this page. I would speculate that Luther, Exposing the Myth probably didn't use Denifle, but rather fished this reference out of Antonin Eymieu, Two Arguments for Catholicism (Burns, Oates and Washbourne, 1928 ) p. 47. They actually mis-cited the reference, as Eymieu cited page 207 (note 4) of Denifle for this quote, and then cited page 404 for an entirely different quote. Luther, Exposing The Myth didn't even lift this quote correctly from a secondary source!

The context for this quote is easy to track down. It's found in WA, Br 2, No. 424 , DeWette 2, 34, and in English in LW 48:277-282. On August 1, 1521 Luther wrote a letter that most scholars think was addressed to Phillip Melanchthon. The letter is now but a fragment. It has no address, salutation, or signature.

Context

If you are a preacher of grace, then preach a true and not a fictitious grace; if grace is true, you must bear a true and not a 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 [in this world] we have to sin. This life is not the dwelling place of righteousness, but, as Peter says, we look for 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 [LW 48:281-282].

Conclusion
I've written an extensive treatment of this quote: Did Luther say, “Be a sinner and sin boldly”? A Look at Justification By Faith Alone and Good Works in Luther’s Theology.

Luther was prone to strong hyperbole. It's his style, and this statement is a perfect example. The first thing to recognize is that the sentence is a statement of comparison. Luther's point is not to go out and commit multiple amounts of gleeful sin everyday, but rather to believe and rejoice in Christ even more boldly despite the sin in our lives. Christians have a real savior. No amount of sin is too much to be atoned for by a perfect savior whose righteousness is imputed to the sinner who reaches out in faith.

But what then is the practical application of sinning “boldly”? What is at the heart of this comparison? Luther explains elsewhere how to take on the attitude of sinning “boldly”:

Therefore let us arm our hearts with these and similar statements of Scripture so that, when the devil accuses us by saying: You are a sinner; therefore you are damned, we can reply: The very fact that you say I am a sinner makes me want to be just and saved. Nay, you will be damned, says the devil. Indeed not, I reply, for I take refuge in Christ, who gave Himself for my sins. Therefore you will accomplish nothing, Satan, by trying to frighten me by setting the greatness of my sins before me and thus seducing me to sadness, doubt, despair, hatred, contempt, and blasphemy of God. Indeed, by calling me a sinner you are supplying me with weapons against yourself so that I can slay and destroy you with your own sword; for Christ died for sinners. Furthermore, you yourself proclaim the glory of God to me; you remind me of God's paternal love for me, a miserable and lost sinner; for He so loved the world that He gave His Son (John 3:16). Again, whenever you throw up to me that I am a sinner, you revive in my memory the blessing of Christ, my Redeemer, on whose shoulders, and not on mine, lie all my sins; for "the Lord hath laid on Him the iniquity of us all" and "for the transgression of His people was He stricken" (Is. 53:6-8). Therefore when you throw up to me that I am a sinner, you are not terrifying me; you are comforting me beyond measure[Ewald Plass, What Luther Says 3:1315].

The strong hyperbolic comparison Luther makes between “sinning boldly” and believing and rejoicing in Christ “even more boldly” comes clear. When assaulted by the fear and doubt of Christ’s love because of previous sins or the remnants of sin in one’s life, one is thrust back into the arms of Christ “on whose shoulders, and not on mine, lie all my sins…”. Rather than promoting a license to sin by saying “sin boldly,” Luther compares the sinner to the perfect savior. Left in our sins we will face nothing but death and damnation. By Christ’s victory over sin, death, and the world, we stand clothed in His righteousness, the recipients of His grace, no matter what we have done.

No historical information exists that indicts Melanchthon of ever murdering or fornicating, even once. The point Luther is making is not to go out and murder or fornicate as much as possible, but rather to point out the infinite sacrifice of Christ’s atonement. There is no sin that Christ cannot cover. His atonement was of an infinite value. That this statement was not to be considered literally is apparent by Luther’s use of argumentum ad absurdum: do people really commit fornication and murder a thousand times a day? No. Not even the most heinous God-hating sinner is able to carry out such a daily lifestyle.

Addendum
Sometimes this quote is cited like this:

If you are a preacher of grace, then preach a true and not a fictitious grace; if grace is true, you must bear a true and not a 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 . . . as long as we are here [in this world] we have to sin. . . . No sin will separate us from the Lamb, even though we commit fornication and murder a thousand times a day.”(Letter to Melanchthon, August 1, 1521, American Edition, Luther’s Works, vol. 48, pp. 281-82)

This is the way Shoebat.com's article, Martin Luther The Bare Truth Unfolded cites it, as well as their article, Martin Luther Was Satanic, If He Were Alive Today He Would Be No Different Than Any Of These Sick Heretics Who Encourage Evil And Sin.  If you find the quote cited this way, the source for this appears to have originally come from Father William Most, Luther's Morals. Most put's forth the quote as follows:

<Letter to Melanchthon>, August 1, 1521 (American Edition, , vol. 48, pp. 281-82, edited by H. Lehmann, Fortress, 1963): "If you are a preacher of grace, then preach a true and not a fictitious grace; if grace is true, you must bear a true [p. 282] and not a fictitious sin. God does not save people who are only fictitious sinners. "(emphasis added).