No one of you should repose hope save in his Lord (Allah); no one of you should fear anything save his sin; no one should feel ashamed of saying "I do not know" when he is asked a matter which he does not know; no one should feel ashamed of learning a thing that he does not know; and you should practise endurance, because endurance is for belief what the head is for the body, so that just as there is no good in a body without the head there is no good in belief without endurance.