يَوۡمَ تَبۡيَضُّ وُجُوهٞ وَتَسۡوَدُّ وُجُوهٞۚ فَأَمَّا ٱلَّذِينَ ٱسۡوَدَّتۡ وُجُوهُهُمۡ أَكَفَرۡتُم بَعۡدَ إِيمَٰنِكُمۡ فَذُوقُواْ ٱلۡعَذَابَ بِمَا كُنتُمۡ تَكۡفُرُونَ ١٠٦
On the Day [some] faces will turn white and [some] faces will turn black. As for those whose faces turn black, [to them it will be said], "Did you disbelieve [i.e., reject faith] after your belief? Then taste the punishment for what you used to reject."
Translation: Saheeh International (English)
Each word's meaning and sound
This great punishment will come upon them on the Day of Judgement, when the faces of those who have faith will become whitened, lighting up with joy and happiness; and the faces of those who denied the truth will become blackened, darkened with sadness and despair. As for those whose faces become blackened on that great day, they will be asked how they could reject faith in Allah alone, and deny the promise they made with Him that they would not worship anything besides Him, when they had had faith and acknowledged it. They will be told to taste the punishment Allah has prepared for them because of their disbelief.
Al-Mukhtasar in interpreting the Noble Quran