Thereafter the verse reads:

وَجَعَلْنَا النَّهَارَ‌ مَعَاشًا (and made the day a source of livelihood....78:11). Man requires, together with sleep, other essentials of life, such as livelihood. Otherwise, the sleep will turn into death. If the world would have had only nights and no days, and man would have continued to sleep all the time, how would he have obtained his livelihood and other essentials, whereas day is the time when he could work hard and make activities in the daylight in order to earn a living. Thus the verses under comment purport to say that Allah has, in order to complete the comforts of life, made the night a cloak and the day for earning a living. وَجَعَلْنَا سِرَ‌اجًا وَهَّاجًا .

Now attention is drawn to the comforts we get from the sky. The most useful thing in the sky is the light of the sun. It is mentioned in the following verse: وَجَعَلْنَا سِرَ‌اجًا وَهَّاجًا . (and created a luminous lamp [ the sun ]....78:13). Then, among the useful things below the sky, the most beneficial and the most essential thing is the raining clouds which are mentioned thus: