It is narrated from Hazrat Hudhaifa (may Allah be pleased with him) that he said: Hearts are of four types. One is the inverted heart; this is the heart of a hypocrite. The heart wrapped in a covering is the heart of a disbeliever. The clear heart, as if a lamp is shining within it, is the heart of a believer. And the heart in which there is both hypocrisy and faith is like a boil in which there is pus and blood, and its example is like a tree that is watered with both polluted and pure water; whichever water prevails over it, it will become like that.