Rav Avigdor Miller on Why We Sleep
Q:
Why did Hashem create sleep if it’s such a waste of time?

A:
Why did He create hunger? It’s a waste of time to eat! Why did He create the necessity to go to the bathroom, it’s a waste of time!

It’s a good question – I’ll tell you why. Hakodosh Boruch Hu made this world for the purpose of recognizing Him. Now, how can people recognize Hashem when they’re so busy in this world? You’re thinking only of your own affairs and you forget about Hashem. So Hashem says, “I’m going to remind you of Me.” And so, you get hungry. You have to eat, you need food, and then when you get a piece of bread: “Oh, I thank You Hashem, what would I do without the bread?! I can’t live without bread.” And the bread causes you to be grateful, to love Hashem, and you’re fulfilling your purpose in the world.

Let’s say, a person is tired; he’s very tired, and his body gets worn out. And now he needs sleep to feel rested. Are you going to just sleep like a cat sleeps? So Hashem says, no. If you’re able to go to sleep, you have to thank Hashem for that. Some people can’t sleep; some people are sick and they can’t sleep. Sleep is a blessing and you have to thank Hashem for the sleep. That’s why He makes you tired. Say it with your mouth: “Ah geshmakeh pleasant night’s sleep!” It’s better than eating the most delicious things! In the morning you get up, and you’re refreshed, you’re a new person. מודה אני לפניך – “I thank You, Hashem.” So the sleep is the for purpose of causing people to be more grateful to Hashem.

That’s only one of the benefits of sleep. There are other benefits too, but this is one of the benefits of sleep that is included in the great program of making people more perfect in this world.