Imam Baqir (A.S) divided the hearts into 3 different categories. First type is the upside down heart, like a vessel, whatever is poured in it will fall out, and this is the heart of the unbeliever, whatever is poured in it will not stay, a heart which is looking for sins in the month of Ramadhan and do not respect the holy month. The second type is a heart which has black spots as well as white spots but these two are in conflict with each other, if whiteness is victorious then it will be blessed otherwise the opposite will be the case. The third type is the heart which is open and a light is lit in it, this type is very precious, this is the sanctuary of God. As the narration says: The heart is the house of God, do not let anti-God enter it.
source : www.tebyan.net