“Never lie to someone who trusts you, and never trust someone who lies to you” is a saying that has been printed on many images. “Never trust someone who lies to you. Never lie to someone who trusts you” was posted on Twitter on August 28, 2009. Authorship is unknown.
 
“‘Never lie to someone who trusts you. Never trust someone who lies to you.’ Watch: http://youtu.be/XpepyJv8ebU #Dexter” was posted on Twitter by Dexter on October 14, 2010. The saying was used in the American television crime drama mystery Dexter on October 17, 2010.
   
“Never lie to someone who trusts you and never trust someone who lies to you. - Deanna Wadsworth” was posted on Twitter on August 3, 2011. However, there is no evidence that author Deanna Wadworth—who first published in 2010—created or popularized the saying.
       
 
Twitter
YAMI
@Yami_D0ll
Never trust someone who lies to you.
Never lie to someone who trusts you.
6:18 PM - 28 Aug 2009
 
Twitter
jay derrell jones
@darealjoka
Never trust someone who lies to you. And Never lie to someone who trusts you.
8:00 PM - 3 Sep 2009
   
Twitter
Dexter
@SHO_Dexter
“Never lie to someone who trusts you. Never trust someone who lies to you.” Watch: http://youtu.be/XpepyJv8ebU #Dexter
3:27 PM - 14 Oct 2010
 
IMDb (The Internet Movie Database)
Dexter (TV Series)
Beauty and the Beast (2010) (Airdate October 17, 2010—ed.)
Quotes
Sonya: [to Dexter resigning as nanny] My mother told me when I was just a little girl, “Never lie to someone who trusts you. Never trust someone who lies to you.” It’s a shame really. We got off to such a good start.
         
Los Angeles (CA) Times
‘Dexter’ recap: Never lie to someone who trusts you; never trust someone who lies to you
OCTOBER 17, 2010 |  9:43 PM
   
Twitter
Sʜoɴ
@ShonMorgen
Never lie to someone who trusts you and never trust someone who lies to you. - Deanna Wadsworth
9:35 AM - 3 Aug 2011
 
Google Books
Things My Daughter Needs to Know
By Dilvin Yasa  
Sydney, Australia: Pan Macmillan Australia Pty Ltd
2012
Pg. ?:
Never lie to someone who trusts you and never trust someone who lies to you.
   
Google Books
Broken Hearts Make Beautiful Words:
Poetry That Touches the Heart
By Danelle Simpson
Xlibris Corporation (Xlibris.com)
2012
Pg. ?:
Never lie to someone who trusts you, And never trust someone who lies to you too.
 
24 June 2012, Canberra (Australia) Times, “Things My Daughter Needs to Know” by Dilvin Yasa. pg. 6:
Never lie to someone who trusts you and never trust someone who lies to you.
   
Google Books
Caught in the Undertow (Hawaiian Crush #6)
By E. L. Todd
Published by author
2014
Pg. ?:
“Never trust someone who lies to you, and never lie to someone who trusts you.”
   
Facebook
Anna Grace Taylor
June 2, 2017 ·
Never lie to someone who trusts you and never trust someone who lies to you.
 
Twitter
Psychology Living
@LivPsy
Never lie to someone who trusts you, and never trust someone who lies to you.
5:00 PM - 1 Apr 2018