أَلَمْ تَرَ إِلَىٰ رَبِّكَ كَيْفَ مَدَّ الظِّلَّ وَلَوْ شَاءَ لَجَعَلَهُ سَاكِنًا ثُمَّ جَعَلْنَا الشَّمْسَ عَلَيْهِ دَلِيلًا (45)
(25:45) Have you not seen how your Lord lengthens out the shadow? Had He willed, He would have made it constant, but We have made the sun its pilot; *58
*58) The word dalil has been used in the sense of the "pilot", who is a person trained to take ships safely in or out of a harbour, or along a waterway. The sun has been trade the pilot of the shadow because the lengthening out of the shadow and its being rolled up depends on the rising, declining and setting of the sun.