Hazrat Muhammad bin Shihab narrates that Hazrat Umar said: Do not pursue that which does not benefit you, and beware of your enemy, and also beware of your friend except for a trustworthy person. For nothing among the people can equal a trustworthy person, and do not keep the company of an evildoer, for he will teach you some of his evil, and do not disclose any of your secrets before him, and in your affairs, seek counsel from those who fear Allah Almighty.