“He causes the break of day and He made the night for rest, and the sun and the moon for the reckoning of time.” (6:97)
“He it is Who has made for you the night dark that you may rest therein, and the day full of light that you may pursue your occupations.” (10:68)
“See they not that We have made the night that they may rest therein, and the day sight-giving? In that verily are Signs for a people who believe.” (27:87)
In relation to these Qur’ānic verses I have quoted:
1.) Many, many scientific studies verify that overall psychological health is better for people who sleep during the night, even if they obtain the same optimal hours of sleep (8 hours for adults) during the day instead. This would apply for instance to college students who pull all-nighters, or to people who work as security guards on graveyard shifts. The Qur’ān is clear about this that the night has been created for sleep.
2.) Melatonin, also known as the “hormone of darkness”, is released in our pineal glands of our brains into our blood as per our Circadian rhythms (sleeping patterns), but are particularly released more in darkness. Melatnonin is the neurohormone that pretty much causes us to sleep (along with other neural factors). People with jet lag or those needing to fix sleep cycles (but unable to do it naturally i.e. by staying awake for extended periods of time and then sleeping) in my opinion should take melatonin pills rather than sleeping pills (which acting as depressants simply lower the heart rate, while a side effect of them is sleep and not the main cause; plus they can be addictive and harmful). What’s interesting is that this represents an evolutionary link in our brains to older forms of life on earth, in which simple animals would have a “light-sensitive eye”. The pineal gland may be the evolutionary form of this. This is all in accordance with the Qur’ān where it outlines that Allah has made the night dark so we may sleep.
3.) Scientists do not have a definitive answer on why we sleep or why it evolutionarily makes sense for us to sleep (we could be caught in a bush sleeping by predators during neanderthal times). Many animals don’t sleep at all (i.e. insects) and some sleep with their eyes open, or standing (i.e. flamingos). So in my opinion, sleep is there for rest (and consolidation of information after studying as well as building muscle tissue), as the Qur’an says, and also…revelation. As a means of God communicating with us. And Dr. Otto Leowi (discoverer of neurotransmission) and Dr. August Kekule (discoverer of benzene), two scientists who had Nobel-prize winning discoveries not from any research but from dreams that they saw, attest to this.