"إن العبد إذا أخطاء خطيئة نكتت في قلبه نكته سوداء فإن هو نزع واستغفر وتاب صقل قلبه وإن عاد زيد فيها حتى تعلو على ¤ قلبه وهو الران الذي ذكر الله تعالى {كَلَّا بَلْ رَانَ عَلَى قُلُوبِهِمْ مَا كَانُوا يَكْسِبُونَ} "
The Prophet (peace and blessings be upon him) said:
"Indeed, when a servant commits a sin, a black spot is placed upon his heart. If he refrains from that sin, seeks forgiveness and repents, his heart is cleaned and polished. But if he returns to sin, that blackness is increased until it covers his whole heart. And this is the rust that Allah Almighty has mentioned (in this verse): 'No! Rather, the rust of what they used to earn has covered their hearts.' [Surah al-Mutaffifin: 14]"
Hadith Referenceصحیح الجامع الصغیر / حرف الألف / 1670
Hadith Gradingالألبانی:حسن
Hadith Takhrij[حم ت ن هـ حب ك هب] عن أبي هريرة. الترغيب ٢/٢٦٨.