look a gift horse in the mouth
US /lʊk ə ɡɪft hɔrs ɪn ðə maʊθ/
UK /lʊk ə ɡɪft hɔrs ɪn ðə maʊθ/
1.
to be ungrateful when receiving a gift or favor by criticizing it
:
•
I know the car isn't new, but don't look a gift horse in the mouth.
•
They offered you a free trip, so don't look a gift horse in the mouth.