Play with an ass, and he will slap your face with his tail.
More Portuguese Proverbs:
Deeds are love, and not sweet words.Portuguese
The ass does not know the value of his tail till he has lost it.
Portuguese
The tired mare goes willingly to grass.
Portuguese
Mouth of honey, heart of gall.
Portuguese
I am on good terms with the friend who eats his bread with me.
Portuguese
The king of the bees has no sting.
Portuguese