Allah (SWT) is the creator of this vast universe and world. Life on this Earth is based on Allah’s manifestations. The greatest and the most manifest of these are the sunrise and sunset, which is coupled with the alteration of day and night. Allah mentioned in the Holy Quran:

Indeed in the alternation of night and day, and in all that Allah has created in the heavens and the earth there are Signs for a God-fearing people. (10:6).

As it is mentioned, the succession of day and night is one of the greatest signs of the Creator. The Quran is the book of God and it contains the signs of the Creator (Allah) and asks the followers to ponder upon them

Another verse of the Holy Quran says.

And He has also subjected to you the sun and the moon, both performing their work constantly. And He has subjected to you the night as well as the day. (Al Quran 14:33)

As the Quran emphatically claims, day time is devoted for work, while the night is for rest.The sun regulates the day while the moon regulates the sleep process.

The Holy Quran mentions the alteration of day and night in 37 places. These verses clearly indicate that the Quran considers humans to be diurnal creatures (i.e. day active) who need light in the daytime and darkness at night.

But, why is it out of God’s mercy that night is for resting and day is for working? Here’s how science explains these verses of the Quran:

In scientific expression, the day night alteration is called circadian rhythm (CR). The term circadian comes from the Latin word circa, meaning “around” (or “approximately”), and diēm, meaning “day” i.e. approximately a day.

The CR is regulated by the clock present inside our body. This is called a biological clock or body clock. Just like an ordinary clock, this clock also tells the time to our body and our body reacts accordingly.

The body clock is divided into 2 parts, the central/master clock (in the brain) and peripheral clocks (in different organs).

The body clock generates the CR and in turn CR regulates the sleep and wake schedule, along with many physiological processes and it repeats roughly every 24 hours. The body clock gets information/cues from sun and moon i.e. presence of light and absence of light. It responds to the cues and tells our bodies when to sleep, rise or eat. It also controls many physiological functions and hormone secretions.

Any disruption or alterations in this cue results in malfunctioning of body clocks, which may results in severe health problems such as sleep deprivation, insomnia, memory impairment, depression, gastro-intestinal disorders and in the long run, these may lead to cancer also.

And among His Signs is your sleep by night, and day for your seeking of His bounty. In that surely are Signs for a people who hear. (Al Quran 30:23)

The body clock inside the human body gets signals from the sunlight and tells our bodies to secrete hormones, to wake up and our bodies respond accordingly. In the morning, just before sunrise, our body gives signals to secrete the Cortisol hormone (commonly known as stress hormone), which peaks in early morning hours. It regulates many metabolic processes (energy giving processes) such as glycolysis which in turn provides us the energy to carry out our activities in day time. This also helps the body to adjust to the stress of day time.

On the contrary, in the night, as the body transits from light to dark, a signal is sent to the body clock that in turn, regulates the secretion of the sleep hormone i.e. melatonin that regulates sleep. Sleep is also one of the most important physiological processes of the human body. Sleep regulates new cell formation, memory consolidation, metabolic and immune functions. One of the striking examples is growth hormone secretion during sleep. Hence, it is important for new born children and kids to sleep more for their proper growth and development. At night, taking rest doesn’t mean only taking a break from the stressful day, but sound sleep also helps our body to reset by replenishing and healing itself to ensure that it can function properly.

The night

On the contrary, in the night, as the body transits from light to dark, a signal is sent to the body clock that in turn, regulates the secretion of the sleep hormone i.e. melatonin that regulates sleep. Sleep is also one of the most important physiological processes of the human body. Sleep regulates new cell formation, memory consolidation, metabolic and immune functions. One of the striking examples is growth hormone secretion during sleep. Hence, it is important for new born children and kids to sleep more for their proper growth and development. At night, taking rest doesn’t mean only taking a break from the stressful day, but sound sleep also helps our body to reset by replenishing and healing itself to ensure that it can function properly.

The scientific studies suggest CR disruption can cause cognitive impairment, poor memory, psychiatric illness, metabolic syndrome, insomnia, depression, slow growth and severe diseases like cancer. Today, a large human population has either chosen to work at night or has been forced to do so in the market economy, and consequently, they are exposing their bodies to artificial light. The light at night misguides our body clock and no sharp transition from light to dark leads to negative consequences on our health.

The Prophet (peace be upon him) encouraged his companions not to be involved in any activity after Isha prayer. He said:
“One should not sleep before the night prayer, nor have discussions after it.”
Additionally, Muslims are required to wake up for Fajr prayer, which is about one hour before sunrise. It was advocated that early morning work is blessed by God.

Human beings are the most important creation of Allah (swt); He created the whole world and all the things on it for humankind. He designed our body to adjust and benefit from the surroundings. Living according to ‘God’s design’ is always beneficial, and being grateful to God means living according to His design.
Allah has in His wisdom spread such signs in each and every manifestation of His to point to the realities that are hidden behind them; but only those people can reach those realities who free themselves from the prejudices of ignorance and acquire righteous knowledge from the sources which Allah has provided.