The old saw says--"let a sleeping dog lie." Experience knows better; experience says, If you want to convince do it yourself.
- Written in Clara Clemens's copy of The Gilded Age

"Let a sleeping dog lie." It is a poor old maxim, & nothing in it: anybody can do it, you don't have to employ a dog.
- Written in copy of Adventures of Huckleberry Finn to Margery Clinton,
18 August 1908

I would rather tell seven lies than make one explanation.
- Letter to John Bellows, 11 April 1883

In all lies there is wheat among the chaff...
- A Connecticut Yankee in King Arthur's Court

Lie -- an abomination before the Lord and an ever present help in time of trouble.
- Speech, 30 March 1901

The lie, as a virtue, a principle, is eternal; the lie, as a recreation, a solace, a refuge in time of need, the fourth Grace, the tenth Muse, man's best and surest friend is immortal.
- "On the Decay of the Art of Lying"

One of the most striking differences between a cat and a lie is that a cat has only nine lives.
- Pudd'nhead Wilson

The most outrageous lies that can be invented will find believers if a man only tells them with all his might.
- Letter to San Francisco Alta California, dated May 17, 1867; published June 16, 1867

[Lying] Man's most universal weakness.
- quoted in Mark Twain and I, by Opie Read

'Tis immoral to lie except for practice.
- Maxim written in copy of Editorial Wild Oats donated in 1905 for the Bryn Mawr book sale. Reported in Washington Times, 16 December 1905, p. 3.

Never tell a lie--P.S. - Except to keep in practice.
- quoted in "Mark Twain's Autograph," Atlanta Constitution, 9 September 1906, p. E3.

Note that venerable proverb: Children and fools always speak the truth. The deduction is plain: adults and wise persons never speak it.
- "On the Decay of the Art of Lying"

You cain't pray a lie.
- Adventures of Huckleberry Finn

Carlyle said "a lie cannot live." It shows that he did not know how to tell them.
- Autobiography of Mark Twain, Volume 2 (2013)

Almost all lies are acts, and speech has no part in them.
- "My First Lie and How I Got Out of It"

Figures often beguile me, particularly when I have the arranging of them myself; in which case the remark attributed to Disraeli would often apply with justice and force: "There are three kinds of lies: lies, damned lies and statistics."
- Autobiography of Mark Twain, Volume 1 (2010)
for more info on the background of this quote, see Stephen Goranson's post to the Mark Twain Forum 31 July 2002

The glory which is built upon a lie soon becomes a most unpleasant incumbrance. . . . How easy it is to make people believe a lie, and how hard it is to undo that work again!
- Autobiographical dictation, 2 December 1906. Published in Autobiography of Mark Twain, Volume 2 (University of California Press, 2013)

"Speak only good of the dead" is a sentimental way of advising the living to lie -- at least as regards the usual run of dead people.
- reprinted in "Bright People in Autograph Albums," Fresno Republican Weekly, 8 March 1884, p. 1 (reprinting from New York World on autographs owned by Mr. Bok)

There are 869 different forms of lying, but only one of them has been squarely forbidden. Thou shalt not bear false witness against thy neighbor.
- Following the Equator; Pudd'nhead Wilson's New Calendar

I am different from Washington; I have a higher, grander standard of principle. Washington could not lie. I can lie, but I won't.
- quoted in Mark Twain, Archibald Henderson

The highest perfection of politeness is only a beautiful edifice, built, from the base to the dome, of graceful and gilded forms of charitable and unselfish lying.
- "On the Decay of the Art of Lying"

The young ought to be temperate in the use of this great art until practice and experience shall give them that confidence, elegance, and precision which alone can make the accomplishment graceful and profitable. Patience, diligence, painstaking attention to detail -- these are the requirements; these, in time, will make the student perfect; upon these, and upon these only, may he rely as the sure foundation for future eminence. Think what tedious years of study, thought, practice, experience, went to the equipment of that peerless old master who was able to impose upon the whole world the lofty and sounding maxim that "Truth is mighty and will prevail"-- the most majestic compound fracture of fact which any of woman born has yet achieved. For the history of our race, and each individual's experience, are sewn thick with evidences that a truth is not hard to kill, and that a lie well told is immortal.
- "Advice to Youth," 15 April 1882

I realize that in a sudden emergency I am but a poor clumsy liar, whereas a fine alert and capable emergency-liar is the only sort that is worth anything in a sick-chamber.
- Autobiographical dictation 7 June 1908, quoting from letter to Joseph Twichell. Published in Autobiography of Mark Twain, Volume 2 (University of California Press, 2013)

It is true I have a passion for lying to rich people, but I do not lie to men who get their bread by thankless hard work.
- Letter to William Dean Howells, 28 October 1889

There is a prejudice against the spoken lie, but none against any other, and by examination and mathematical computation I find that the proportion of the spoken lie to the other varieties is 1 to 22,894. Therefore the spoken lie is of no consequence, and it is not worth while to go around fussing about it and trying to make believe that it is an important matter. The silent colossal National Lie that is the support and confederate of all the tyrannies and shams and inequalities and unfairnesses that afflict the peoples - that is the one to throw bricks and sermons at.
- "My First Lie and How I Got Out of It"

Anybody can tell lies: there is no merit in a mere lie, it must possess art, it must exhibit a splendid & plausible & convincing probability; that is to say, it must be powerfully calculated to deceive.
- "The Ashcroft-Lyon Manuscript." Published in Autobiography of Mark Twain, Volume 3 (University of California Press, 2015)

Let others lie, wantonly, gratuitously, if they will, but let you & me make it the rule of our life to lie for revenue only.
- manuscript page dated 15 January 1910 from the Ethel Sloan collection

A lie can travel halfway round the world while the truth is putting on its shoes.
- This quote has been attributed to Mark Twain, but it did not originate with him. Charles Haddon Spurgeon (1834-92) attributed it to an old proverb in a sermon delivered on Sunday morning, April 1, 1855. Spurgeon was a celebrated English fundamentalist Baptist preacher. His words were: "A lie will go round the world while truth is pulling its boots on." Even earlier, in 1710 Jonathan Swift wrote on the same topic in The Examiner.

The results of an extensive search for the genesis of this quote and its variations was published online in July 2014 at QUOTE INVESTIGATOR.