“The person whose doors I enter with most pleasure, and quit with most regret, never did me the smallest favour.”

Source: The Picture of Dorian Gray

Source: Dead of Winter

The Age for Love
Context: I bore with the ill-humor of my chief. What would he have said if he had known that I had in my pocket an interview and in my head an anecdote which were material for a most successful story? And he has never had either the interview or the story. Since then I have made my way in the line where he said I should fail. I have lost my innocent look and I earn my thirty thousand francs a year, and more. I have never had the same pleasure in the printing of the most profitable, the most brilliant article that I had in consigning to oblivion the sheets relating my visit to Nemours. I often think that I have not served the cause of letters as I wanted to, since, with all my laborious work I have never written a book. And yet when I recall the irresistible impulse of respect which prevented me from committing toward a dearly loved master a most profitable but infamous indiscretion, I say to myself, "If you have not served the cause of letters, you have not betrayed it." And this is the reason, now that Fauchery is no longer of this world, that it seems to me that the time has come for me to relate my first interview. There is none of which I am more proud.

Source: Hitler: A Biography (1936), p. 58

Source: Atlas Shrugged

Comment of late 1788 or early 1789 upon his slaves http://www.mountvernon.org/george-washington/slavery/the-only-unavoidable-subject-of-regret/, as recorded by David Humphreys, in his notebooks on his conversations with Washington, now in the Rosenbach Library in Philadelphia<!-- as quoted in "Housing and Family Life of the Mount Vernon Negro," unpublished paper by Charles C. Wall, prepared for the Mount Vernon Ladies' Association (May 1962), prefatory note]. -->
1780s
Context: The unfortunate condition of the persons, whose labour in part I employed, has been the only unavoidable subject of regret. To make the Adults among them as easy & as comfortable in their circumstances as their actual state of ignorance & improvidence would admit; & to lay a foundation to prepare the rising generation for a destiny different from that in which they were born; afforded some satisfaction to my mind, & could not I hoped be displeasing to the justice of the Creator.

Kerin, in Book Seven : What Saraïde Wanted, Ch. XLII : Generalities at Ogde
The Silver Stallion (1926)

Attributed in Lincoln the Lawyer (1906) by Frederick Trevor Hill — Hill noted that he could find no record of whom Lincoln was insulting.
Posthumous attributions