Look not a gift horse in the mouth.
More Spanish Proverbs:
My neighbour's hen lays more eggs than mine.Spanish
Do not stuff your servant with bread, and he won't ask for cheese.
Spanish
When thou seest thy house in flames, go warm thyself by it.
Spanish
When thou seest thy house in flames, go warm thyself by it.
Spanish
He that would have a beautiful wife should choose her on a Sunday.
Spanish
The cross on his breast, and the devil in his heart.
Spanish