Tafsir of Al-Hajj 22:61

{ ذالك } That victory is because He is All-Powerful. Among the signs of His absolute power is that:

{ يُولِجُ اللَّيْلَ فِي النَّهَارِ وَيُولِجُ النَّهَارَ فِي اللَّيْلِ } Or, it is because He is the Creator of the night and the day and the One who alternates them. Nothing that occurs within them—by the hands of His servants, whether good or evil, oppression or justice—is hidden from Him.

{ وَأَنَّ اللَّهَ هُوَ السَّمِيعُ } To what they say.

{ الْبَصِيرُ } To what they do.

If you ask: What is the meaning of inserting one of the two periods into the other?

I say: It is the attainment of the darkness of one in the place of the light of the other through the setting of the sun, and the light of one in the place of the darkness of the other through its rising—just as a tunnel is illuminated by a lamp and darkened by its absence. It is also said: It refers to the increase in the hours of one by what is decreased from the other.

{ ذَٰلِكَ بِأَنَّ اللَّهَ هُوَ الْحَقُّ وَأَنَّ مَا يَدْعُونَ مِن دُونِهِ هُوَ الْبَاطِلُ وَأَنَّ اللَّهَ هُوَ الْعَلِيُّ الْكَبِيرُ }