I wonder at those who protect themselves against having harmful food, how do they not protect themselves from committing sins so that they will be saved from Hell? I wonder at those who purchase slaves with their money, why do they not purchase the free through doing favors to them? Good and evil cannot be recognized with any means other than people. If you want to recognize good, you should do it so as to know its people, and if you want to recognize evil, you should do it so as to know its people.
— ALI IBN ABI TALIB