There is no believing a liar, even when he speaks the truth.
 Aesop, Aesop's Fables. copy citation

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Author Aesop
Source Aesop's Fables
Topic truth
Date
Language English
Reference
Note Translated by George Fyler Townsend
Weblink http://www.gutenberg.org/files/21/21-h/21-h.htm

Context

““Pray, do come and help me; the Wolf is killing the sheep;” but no one paid any heed to his cries, nor rendered any assistance. The Wolf, having no cause of fear, at his leisure lacerated or destroyed the whole flock. There is no believing a liar, even when he speaks the truth. The Cat and the Birds A CAT, hearing that the Birds in a certain aviary were ailing dressed himself up as a physician, and, taking his cane and a bag of instruments becoming his profession, went to call on them.” source