Wamin ayatihi manamukum billayli wannahari wabtighaokum min fadlihi inna fee thalika laayatin (surah Rum: 23)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(30:23) And of His Signs is your sleeping at night and your seeking His Bounty *33 during the day. Indeed there are Signs in this for those who hearken.

Wa min Aayaatihee manaamukum bil laili wannahaari wabtighaaa`ukum min fadlih; inna fee zaalika la Aayaatil liqawminy yasma`oon

*33) "To seek bounty" is to seek the livelihood. Though man generally sleeps at night and works for his living in the day, this is not a law. Many people also sleep in the day and work for their livelihood at night. That is why the night and the day both have been mentioned and it has been said: "In both day and nights you sleep as well as work for your livelihood. " This also is a Sign which points to the design of the Wise Creator: Furthermore, it also points to the fact that He is not merely a Creator but also extremely Compassionate and Merciful to His creations, and is more anxious than the creation to meet its needs and requirements. Man cannot constantly labour but needs to have a rest of a few hours after every few hours of hard work so as to rebuild energy to take up work again. For this purpose, the Wise and Merciful Creator has not rested content with creating a feeling of fatigue and a desire for rest in man, but has placed in his nature a powerful urge for the "sleep", which without his will, even inspite of resistance from him, overpowers him automatically after every few hours of work and wakefulness, and compels him to have a few hours of rest, and leaves him as soon as the need has been fulfilled. Man has so far been unable to understand the naturer and real causes of the sleep. This is something wholly innate, which has been placed in the nature and structure of man. Its being` precisely according to the requirements of man is enough to testify that it is not anything accidental, but has been provided by a Wise Being in accordance with a purpose and plan. It is based on a clear wisdom and reason and purposefulness. Moreover, the sleep itself testifies that the One Who has placed this compulsive urge in man is a greater well wisher of man than man himself, otherwise man would have deliberately resisted the sleep and endeavoured to keep constantly awake and worked continuously hard and thus exhaust not only his work-power but also his vital powers.
Then, by using the word "seeking Allah's bounty" for the seeking of livelihood, allusion has been made to another series of the Signs. How could have man sought and found his `livelihood if the innumerable and unlimited forces of the earth and heavens had not been put to work to provide means of the livelihood and supply countless resources for man to seek it in the earth? Not only this. Man could not have exploited these means and resources had he not been given appropriate limbs and suitable physical and mental capabilities for the purpose. Thus the ability in man to seek the livelihood and the presence of the resources of the livelihood outside of him, clearly indicate the existence of a Merciful and Beneficent God. An intellect which is not sick can never presume that all this has happened by chance, or is the manifestation of the godhead of many gods, or some merciless, blind force is responsible for these bounties and blessings.