Hazrat Abu Al-Bakhtari (may Allah have mercy on him) narrates that Hazrat Hudhaifa (may Allah be pleased with him) said: There are four types of hearts. One is the heart in which there is deceit; this is the heart of a hypocrite. One is the heart that is wrapped in a covering; this is the heart of a disbeliever. One is the heart that is clear and from which light shines forth; this is the heart of a believer. One is the heart in which there is both hypocrisy and faith. Its example is like a boil in which there is pus and blood. Its example is like a tree that receives both clean and dirty water; whichever water prevails, its effect will be seen in it.