47 If you've ever wanted to take back anything you wrote that is in print . . .

. . .[I beseech you] to read my earliest books very
circumspectly and with much pity, knowing that before now I too was a monk, and one of the right frantic and raving papists. When I took up this matter against Indulgences, I was so full and drunken, yea, so besotted in papal doctrine that, out of my great zeal, I would have been ready to do murder -- at least, I would have been glad to see and help that murder should be done -- on all who would not be obedient and subject to the pope, even to his smallest word. . . .

I tell these things to the end that, if thou shalt read my books, thou mayest know and remember that I am one of those who, as St. Augustine says of himself, have grown by writing and by teaching others, and not one of those who, starting with nothing, have in a trice become the most exalted and most learned doctors. We find, alas! many of these self-grown doctors; who in truth are nothing, do nothing and accomplish nothing, are moreover untried and inexperienced, and yet, after a single look at the Scriptures, think themselves able wholly to exhaust its spirit.

Dr. Martin Luther, 1545

Published in: Works of Martin Luther Adolph Spaeth, L.D. Reed, Henry Eyster Jacobs, et al., Trans. & Eds. (Philadelphia: A. J. Holman Company, 1915), Vol. 1, pp. 10-11.
http://www.iclnet.org/pub/resources/text/wittenberg/luther/luther-reader.txt