never look a gift horse in the mouth
If?you?receive?a?gift,?do?so?graciously,?without?voicing?criticisms.?The?saying?is?attributed?to?St.?Jerome?and?refers?to?the practice?of?looking?at?a?horse's?teeth?to?determine?its?age. I know Aunt Jean isn't your favorite person, but she gave you that beautiful sweater as a present, and you should never look a gift horse in the mouth! A: "But I don't want this ancient car!" B: "Never look a gift horse in the mouth, OK? You're so lucky to get a car for free!"