Surah Al-Anbya 21:30

أَوَلَمْ يَرَ ٱلَّذِينَ كَفَرُوٓا۟ أَنَّ ٱلسَّمَـٰوَٰتِ وَٱلْأَرْضَ كَانَتَا رَتْقًا فَفَتَقْنَـٰهُمَا ۖ وَجَعَلْنَا مِنَ ٱلْمَآءِ كُلَّ شَىْءٍ حَىٍّ ۖ أَفَلَا يُؤْمِنُونَ

Have those who disbelieved not considered that the heavens and the earth were a joined entity, and then We separated them and made from water every living thing? Then will they not believe?

Translation: Saheeh International

Tafsir

Have they not one may read a-wa-lam or a-lam realised have they not come to know those who disbelieve that the heavens and the earth were closed together and then We parted them We made seven heavens and seven earths — or it is meant that the heaven was parted and began to rain when it did not use to do so and that …

Excerpt from Tafsir al-Jalalayn, commentary on 21:30, via Quran.com. The reader has the full commentary and 9 more tafsirs.