Quran 72:8

وَأَنَّا لَمَسْنَا ٱلسَّمَآءَ فَوَجَدْنَٰهَا مُلِئَتْ حَرَسًۭا شَدِيدًۭا وَشُهُبًۭا

And we have sought [to reach] the heaven but found it filled with powerful guards and burning flames.

Translation · Saheeh International