God forbid: yea, let God be true, but every man a liar.

-Bible (NewTestament)
Romans 3:4.

Young as he was, his instinct told him that the best liar is he who makes the smallest amount of lying go the longest way.

-Butler, Samuel
  The Way of  All Flesh, ch.39.

A great partyought nottobe brought down because of a squalid affair between a woman of easy virtue and a proved liar.

-Hailsham, Quintin (McGarel) Hogg, 2nd Viscount
  On the Profumo affair, BBC  T V,13  Jun.

It is always the best policy to speak the truthöunless, of course, you are an exceptionally good liar.

-Jerome,Jerome K(lapka)
  In The Idler (edited by Robert Barr and Jerome), Feb.

Il n'e¤  tait pas menteur, il avouait la ve¤  rite¤   et disait qu'il e¤  tait cruel. He was not a liar. He admitted the truth and said that he was cruel.

-Lautre¤  amont, Comte de properly Isidore Ducasse
  Les Chants de Maldoror, pt.1.

El amor siempre fabla mentiroso. Love is always a liar.

-Ruiz,Juan
c.1330  Libro de Buen Amor, stanza161.

A man who lies, thinking it is the truth, is an honest man, and a man who tells the truth, believing it to be a lie, is a liar.

-Safire,William
  After the Fall, referring toWatergate and the resignation of Richard M Nixon.

'I believe I take precedence,' he said coldly; 'you are merely the Club Bore: I am the Club Liar.'

-Saki pseudonym of  Hector Hugh Munro
  Beasts and Super-Beasts,'A Defensive Diamond'.

An experienced, industrious, ambitious, and often quite picturesque liar.

-Twain, Mark pseudonym of  Samuel Langhorne Clemens
  'The Private History of a CampaignThat Failed'.

The only thing worse than a liar is a liar that's also a hypocrite!

-Williams,TennesseeThomas Lanier
  Rosa.The RoseTattoo, act 3.