The phrase “don’t look a gift horse in the mouth” means that one should not criticize or be ungrateful for a gift or something that is freely given. The expression originates from the practice of examining a horse’s teeth to determine its age and health. If someone receives a horse as a gift, inspecting its mouth to check its value would be seen as impolite and ungrateful.
In essence, the saying advises people to accept gifts graciously without questioning their worth or quality. It encourages a mindset of appreciation rather than skepticism or entitlement.