The following is from Luther's dissertation on the Keys. It is common, and an error, to preach the gospel in such a way that it does not freely reach the ungodly, sinning sinner, but places conditions on it, such as a proper repentance or reformation of life. The awakened see nothing in themselves by which God should show favor, but see only sin and God's judgment because of their very real sin. Therefore we must preach the gospel in such a way that even ungodly thieves and harlots can enter in.
[Pope] "What should we give you?"
[Pope] "But is absolution really certain? In case you repent and if our absolution is valid in heaven, then you are absolved; if not, you are not absolved. For the key can miss."
[Luther] "Here I am again told that the key depends upon my repentance and worthiness before God. And I can become such a skilful locksmith with my repentance that I can manufacture for my Lord God from his (selection of) keys both right and wrong keys. If I repent I make his key the right one; if I do not repent I make of it the wrong one. That is to say, if I repent then God is truthful, if I do not he lies. Things are going along real well! But how do I know whether my repentance and worthiness before God are sufficient? Shall I stand there, open-mouthed, gaping toward heaven and wait until I learn and become convinced that my repentance is sufficient? When will I really get to know?"
[Pope] "You have to worry about that."
LW AE vol 40 pp 339, 340
The third result of such teaching is the establishment of human endeavor and self-righteousness in opposition to the righteousness of Christ, given to us by grace through faith. In this matter one can forcefully convict them because of their abomination. For with their spurious keys they not only destroy God's Word, but also distract people from God's Word, referring them to their own works and merits, saying, if you are repentant and pious and upright the keys will benefit you, otherwise not. Is not this to say, you must earn grace and become worthy of the same through you own works before God, and then the keys also will benefit you? Tell me how could one more thoroughly leave a Christian to his own works and entice him to a reliance upon his own merits, thus driving him farther away from God's mercy and Christ's blood, than with such a teaching? Further, they teach us how to turn God into a false judge who is a respecter of persons and is bound to look upon our own works favorably, thereby selling his grace instead of giving it freely through his mercy. If I am first to earn grace before God with my own endeavors, of what use, in the devil's name, are the keys to me, since they cannot give me grace unless I have earned it first before God? But if I forst obtain grace I need heed neither keys nor pope. For, "If God is for us, who is against us?" [Rom 8:31].
LW AE vol 40 p 349