فَكَذَّبُوهُ فَأَخَذَهُمْ عَذَابُ يَوْمِ ٱلظُّلَّةِ ۚ إِنَّهُۥ كَانَ عَذَابَ يَوْمٍ عَظِيمٍ
Fakazzaboohu fa akhazahum 'azaabu Yawmiz zullah; innahoo kaana 'azaaba Yawmin 'Azeem
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.
So they denied him, and the punishment of the day of the overshadowing cloud seized them — truly, it was the punishment of a tremendous day.