Italy
A CAVAL DONATO NON SI GUARDA IN BOCCA
Translation: You must not look a gift horse in the mouth. Einem geschenkten Gaul schaut man nicht ins Maul
Use: When you reach something very easily and without any trouble, be satisfated and don’t ask more.
Meaning: To estimate the value of a horse you have to open his mouth and look at his deeths, so if you have already the horse and you use it, it is not the case.