To look a gift horse in the mouth
Related to To look a gift horse in the mouth: don't look a gift horse in the mouth
|to examine the mouth of a horse which has been received as a gift, in order to ascertain his age; - hence, to accept favors in a critical and thankless spirit.|
See also: Horse
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.