Reveal not every secret you have to a friend, for how can you tell but that friend may hereafter become and enemy. And bring not all mischief you are able to upon an enemy, for he may one day become your friend.
All human beings are limbs of the same body. God created them from the same essence. If one part of the body suffers pain, then the whole body is affected. If you are indifferent to this pain, you cannot be called a human being.
However much you study, you cannot know without action. A donkey laden with books is neither an intellectual nor a wise man. Empty of essence, what learning has he whether upon him is firewood or book?
