Ayah 4:

وَاللَّيْلِ إِذَا يَغْشَاهَا


and I swear by the night as it covers it [the light of the sun] up.

All these Oaths are Surrounded around the Sun:

With the sun which gives its light so that we appreciate the Day [Ayah 1], and the light of the sun which reflects on the moon to help us through the night [Ayah 2]. With the light of the sun with its beauty and glory [Ayah 3]. And the night which covers the sun’s brightness. [Ayah 4].

In this surah, Allah will make a parallel between the Sun and the Nafs (roughly translated as Conscience).

How the sun has different things that happen to it through conflict, and how the nafs has different things happen to it through conflict.