Surah Al-Hadid 57:6

يُولِجُ ٱلَّيْلَ فِى ٱلنَّهَارِ وَيُولِجُ ٱلنَّهَارَ فِى ٱلَّيْلِ ۚ وَهُوَ عَلِيمٌۢ بِذَاتِ ٱلصُّدُورِ

He causes the night to enter the day and causes the day to enter the night, and He is Knowing of that within the breasts.

Translation: Saheeh International

Tafsir

He makes the night pass into He makes it enter the day so that it increases while the night diminishes and makes the day pass into the night so that it increases while the day diminishes. And He is Knower of what is in the breasts of what it contains of secrets and convictions.

Excerpt from Tafsir al-Jalalayn, commentary on 57:6, via Quran.com. The reader has the full commentary and 9 more tafsirs.