It is useless to work so hard for a living, getting up early and going to bed late. For the Lord God provides for those he loves while they sleep.
Psalms 127: 2

Blessings on Him who invented sleep, the mantel that covers all human thoughts, the food that satisfies hunger, the drink that slakes thirst, the fire that warms cold, the cold that moderates heat and lastly, the common currency that buys all things, the balance and weight that equalizes the shepherd and the king, the simpleton and the sage.
Cervantes, Don Quixote

Sleep is the only medication that gives ease.
Sophocles

Up sluggard, there'll be time enough for sleeping in the grave.
Benjamin Franklin

The greatest healer of all is good, restful sleep. Whenever you're tired, ill or feeling down and out, go to sleep and let nature revitalize you. It's the only real natural miracle cure around.

Sleep is necessary to recharge and repair the body and the brain. Everybody needs a certain, minimal amount.

If you don't get enough, the hormones and neurotransmitters in the brain will be worn out and sluggish and could take over at anytime causing you to fall into a necessary sleep to recharge the brain even if only for a few seconds.

Melatonin is a hormone released when the sun sets in the absence of light to make you feel sleepy. Youe body and brain slow down. Your brain waves go from full consciousness beta waves to alpha waves to theta waves.

It is estimated that 100,000 accidents in the U.S. every year are due to people falling asleep behind the wheel. A solution is to take quick, short naps during the day. There is currently a drug in the research stages that will be able to fool the brain into thinking it's had enough sleep.

Sleep is the recuperation of energy.

Sleep repairs the wear and tear of the body and mind.

During sleep most of the functions of the body operate at a minimal level, enabling rest.

The oldest theory of sleep, the ischemic theory, is that sleep is induced by a reduction in the blood supply to the brain or at least to conscious centres.

The chemical theory says the body fills up with waste and toxins during the day up to the point where it needs sleep to dispose of them.

Another theory places sleep under the control of the hypothalamus.

Women generally sleep from 45 minutes to one hour more than men.