﴿ أَوْ تُسْقِطَ ٱلسَّمَآءَ كَمَا زَعَمْتَ عَلَيْنَا كِسَفًا أَوْ تَأْتِىَ بِٱللَّهِ وَٱلْمَلَٰٓئِكَةِ قَبِيلًا ﴾

“or thou cause the skies to fall down upon us in smithereens, as thou hast threatened, or [till] thou bring God and the angels face to face before us,”

Please check ayah 17:93 for complete tafsir.