Surah Al-Jinn, ayah 8

وَأَنَّا لَمَسۡنَا ٱلسَّمَآءَ فَوَجَدۡنَٰهَا مُلِئَتۡ حَرَسٗا شَدِيدٗا وَشُهُبٗا ٨

Wa annā lamasnas-samā'a fawajadnāhā muli'at harasan shadīdan washuhubā

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