Surah An-Naba 78:12

وَبَنَيْنَا فَوْقَكُمْ سَبْعًا شِدَادًا

And constructed above you seven strong [heavens].

Translation: Saheeh International

Tafsir

and built above you seven mighty ones? seven heavens shidād is the plural of shadīda that is to say strong and sturdy unaffected by the passage of time

Excerpt from Tafsir al-Jalalayn, commentary on 78:12, via Quran.com. The reader has the full commentary and 9 more tafsirs.