198 – ʿAbd Allāh ibn Abī Badr narrated to me; al-Walīd ibn Muslim narrated to us; Muḥammad ibn ʿAjlān narrated to us; al-Qaʿqāʿ ibn Ḥakīm narrated to me, from Abū Ṣāliḥ, from Abū Hurayrah, who reported that the Prophet ﷺ said:

“When a servant commits a sin, a black spot is placed upon his heart. If he repents, the heart is polished clean; but if he persists, the spot grows until his entire heart becomes black.”

He then said, “That is the meaning of Allah’s statement: ‘No indeed; rather, what they were earning has rusted over their hearts’ (al-Muṭaffifīn 14).”