26:189
فَكَذَّبُوهُ فَأَخَذَهُمْ عَذَابُ يَوْمِ ٱلظُّلَّةِ ۚ إِنَّهُۥ كَانَ عَذَابَ يَوْمٍ عَظِيمٍ
fakadhabūhu fa-akhadhahum ʿadhābu yawmi l-ẓulati innahu kāna ʿadhāba yawmin ʿaẓīmin
They called him a liar, and so the torment of the Day of Shadow came upon them- it was the torment of a terrible day.
But they belied him, so the torment of the day of shadow (a gloomy cloud) seized them. Indeed that was the torment of a Great Day.