An act from which you get no benefit that costs you. No good deed goes unpunished. A good deed will come back and bite you in the ass.
Goring issued an order shielding decorated Jewish WW1 veterans and their families from the Gestapo. That order was used against Goring at his trial. His good deed came back and bit him in the ass.
by knowman March 16, 2008
... ask the Wizard of Oz from the Metro-Goldwyn-Mayer Hollywood classic 1939 major motion picture starring Judy Garland. After Dorothy's little dog, Toto has pulled the curtain by exposing him as another, average, mortal human-being.
The Wizard then uses 'Good Deed Doer' as a definition of character when he's presenting the earned honors and awards of valor to the Tin Woodsman, the Cowardly Lion and the Scarecrow near the end of the much-celebrated favorite.
by OzMoses February 28, 2012