(V.83:14) Narrated Abu Hurairah رضي الله عنه: Allâh’s Messenger صلى الله عليه وسلم said, "When a slave (a person) commits a sin (an evil deed) a black dot is dotted on his heart. Then if that person gives up that evil deed (sin), begs Allâh to forgive him, and repents, then his heart is cleared (from that heart covering dot); but if he repeats the evil deed (sin), then that covering is increased till his heart is completely covered with it. And that is Ar-Rân which Allâh mentioned (in the Qur’ân), "Nay! but on their hearts is the Rân (covering of sins and evil deeds) which they used to earn." (At-Tirmidhi, Vol.5, Hadith No.3334).
(V.83:34) Narrated Anas bin Mâlik رضي الله عنه: A man said, "O Allâh’s Prophet! Will Allâh gather a disbeliever (prone) on his face on the Day of Resurrection?" He صلى الله عليه وسلم said, "Will not the One Who made him walk on his feet in this world, be able to make him walk on his face on the Day of Resurrection?" (Qatâdah, a subnarrator, said: "Yes, By the Power of Our Lord!") (Sahih Al-Bukhari, Vol.6, Hadith No.283).