“He who permits himself to tell a lie once, finds it much easier to do it a second and third time, till at length it becomes habitual; he tells lies without attending to it, and truths without the world's believing him. This falsehood of tongue leads to that of the heart, and in time depraves all its good dispositions.”

Aristotle, 9.
The Lives and Opinions of Eminent Philosophers (c. 200 A.D.), Book 5: The Peripatetics

Harry Potter in Ch. 65 http://www.fanfiction.net/s/5782108/65/Harry_Potter_and_the_Methods_of_Rationality
Harry Potter and the Methods of Rationality (2010 - 2015)
Context: Lies propagate, that’s what I’m saying. You’ve got to tell more lies to cover them up, lie about every fact that’s connected to the first lie. And if you kept on lying, and you kept on trying to cover it up, sooner or later you’d even have to start lying about the general laws of thought. Like, someone is selling you some kind of alternative medicine that doesn’t work, and any double-blind experimental study will confirm that it doesn’t work. So if someone wants to go on defending the lie, they’ve got to get you to disbelieve in the experimental method. Like, the experimental method is just for merely scientific kinds of medicine, not amazing alternative medicine like theirs. Or a good and virtuous person should believe as strongly as they can, no matter what the evidence says. Or truth doesn’t exist and there’s no such thing as objective reality. A lot of common wisdom like that isn’t just mistaken, it’s anti-epistemology, it’s systematically wrong. Every rule of rationality that tells you how to find the truth, there’s someone out there who needs you to believe the opposite. If you once tell a lie, the truth is ever after your enemy; and there’s a lot of people out there telling lies.

Source: Resurrection (1899), Ch. 28

cited in: Andrea Varsavsky, ‎Iven Mareels, ‎Mark Cook (2010). Epileptic Seizures and the EEG. p. 89

The Essays Or Counsels, Civil And Moral, Of Francis Ld. Verulam Viscount St. Albans (1625), Of Simulation And Dissimulation

Letter to Allen N. Ford (11 August 1846), reported in Roy Prentice Basler, ed., Abraham Lincoln: His Speeches and Writings (1990 [1946])
1840s

Source: His Dark Materials, The Subtle Knife (1997), Ch. 4 : Trepanning
Context: Lyra sighed; she had forgotten how roundabout Scholars could be. It was difficult to tell them the truth when a lie would have been so much easier for them to understand.