“I often think of death.
True.
Suicide is a reasonable option.
True.
My sins are unpardonable.
I stare at the question.
My sins are unpardonable.
I stare at the question.
My sins are unpardonable.
I leave it blank.”

The Devil's Dictionary (1911)

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 553.

Source: Magick: Liber ABA: Book 4

"Ethan Brand" (1850)

On the advisableness of improving natural knowledge (1866) http://www.gutenberg.org/dirs/etext01/thx1410.txt
1860s
Context: The improver of natural knowledge absolutely refuses to acknowledge authority, as such. For him, scepticism is the highest of duties; blind faith the one unpardonable sin. And it cannot be otherwise, for every great advance in natural knowledge has involved the absolute rejection of authority, the cherishing of the keenest scepticism, the annihilation of the spirit of blind faith; and the most ardent votary of science holds his firmest convictions, not because the men he most venerates hold them; not because their verity is testified by portents and wonders; but because his experience teaches him that whenever he chooses to bring these convictions into contact with their primary source, Nature — whenever he thinks fit to test them by appealing to experiment and to observation — Nature will confirm them. The man of science has learned to believe in justification, not by faith, but by verification.

Medium Raw (2010)
Source: Medium Raw: A Bloody Valentine to the World of Food and the People Who Cook

"A Conversation with William Styron", Humanities (May/June 1997)

Dans un mois, dans un an (1957, Those Without Shadows, translated 1957)

in response to the question, "Is adultery a sin."
in the New York Post, February 23, 1990, as archived at the Daily Beast http://www.thedailybeast.com/articles/2016/10/30/donald-trump-in-1990-adultery-is-not-a-sin.html
1990s