﴿ أَوَلَمْ يَرَ ٱلَّذِينَ كَفَرُوٓا۟ أَنَّ ٱلسَّمَٰوَٰتِ وَٱلْأَرْضَ كَانَتَا رَتْقًۭا فَفَتَقْنَٰهُمَا ۖ وَجَعَلْنَا مِنَ ٱلْمَآءِ كُلَّ شَىْءٍ حَىٍّ ۖ أَفَلَا يُؤْمِنُونَ ﴾

“ARE, THEN, they who are bent on denying the truth not aware that the heavens and the earth were [once] one single entity, which We then parted asunder? – and [that] We made out of water every living thing? Will they not, then, [begin to] believe?”

Please check ayah 21:33 for complete tafsir.