“When a muslim sins, a black dot appears in his heart and then when he does taubah and istighfaar, his heart is cleansed (of the black spot). And when he sins more, the spot enlarges till it covers the entire heart.”

Hence this is the rust which Allaah has mentioned in the Holy Quraan thus: “By no means! But what they have earned is rust upon their hearts.” [83:14]


[Masnad Imam Ahmad bin Hanbal]