يُولِجُ الَّيْلَ فِى النَّهَارِ وَيُولِجُ النَّهَارَ فِى الَّيْلِ
(He merges night into day, and merges day into night,) meaning, He does what He wills with His creatures. He alternates the night and day and measures them by His wisdom, as He wills. Sometimes, He makes the night longer than the day, and sometimes the opposite. Sometimes, He makes the length of night and day equal. Sometimes, He makes the season winter, then changes it to spring, then summer then autumn. All this He does by His wisdom and His due measure of everything in His creation,