Don't look a gift horse in the mouth

The phrase "Don't look a gift horse in the mouth" means that when one receives a gift or favor, they should not question or criticize its value or merits. This phrase is derived from the practice of examining a horse's teeth to determine its age and overall health. Looking a gift horse in the mouth would imply suspicion or ingratitude toward the gift, which can be considered rude or unappreciative. Thus, it is advisable to accept and appreciate a gift without scrutinizing its worth.