Why do we need sleep? For some people, it seems like a defect. If God created us perfect, then why make us waste a third of our lives lying unconscious. John Piper, in A Brief Theology of Sleep has an interesting answer:
Psalm 127:2 says, “It is in vain that you rise up early and go late to rest, eating the bread of anxious toil; for he gives to his beloved in his sleep.” According to this text sleep is a gift of love, and the gift is often spurned by anxious toil. Peaceful sleep is the opposite of anxiety. God does not want his children to be anxious, but to trust him. Therefore I conclude that God made sleep as a continual reminder that we should not be anxious but should rest in him.
Sleep is a daily reminder from God that we are not God. “He who keeps Israel will neither slumber nor sleep” (Psalm 121:4). But Israel will. For we are not God. Once a day God sends us to bed like patients with a sickness. The sickness is a chronic tendency to think we are in control and that our work is indispensable. To cure us of this disease God turns us into helpless sacks of sand once a day.
God wants to be trusted as the great worker who never tires and never sleeps. He is not nearly so impressed with our late nights and early mornings as he is with the peaceful trust that casts all anxieties on him and sleeps.