A man asked Muhammad what was the mark whereby he might know...

A man asked Muhammad what was the mark whereby he might know the reality of his faith. Muhammad said, 'If thou derive pleasure from the good which thou hast performed and thou be grieved for the evil which thou hast committed, thou art a true believer.' The man said. 'In what doth a fault really consist' Muhammad said, 'when action pricketh thy conscience, forsake it.'