ذٰلِكَ بِأَنَّ اللَّهَ يولِجُ اللَّيلَ فِي النَّهارِ وَيولِجُ النَّهارَ فِي اللَّيلِ وَأَنَّ اللَّهَ سَميعٌ بَصيرٌ

That is because Allah causes the night to enter the day and causes the day to enter the night and because Allah is Hearing and Seeing.