﴿ فَكَذَّبُوهُ فَأَخَذَهُمْ عَذَابُ يَوْمِ ٱلظُّلَّةِ ۚ إِنَّهُۥ كَانَ عَذَابَ يَوْمٍ عَظِيمٍ ﴾

“But they gave him the lie. And thereupon suffering overtook them on a day dark with shadows: and, verily, it was the suffering of an awesome day!”

But they denied him so they were seized by the chastisement of the day of the shade al-zulla — a cloud which gave them shade when they suffered a bout of extreme heat but which then rained down fire on them and they were incinerated. Assuredly it was the chastisement of a tremendous day.