If you're like me, at some point Sunday evening you begin to consider all the opportunities and challenges that await you in the coming week. Fruitful labor in our calling is a gift from God — indeed, we are to "work heartily, as for the Lord" (Colossians 3:23). But at the close of each day, we must learn to entrust our work and circumstances to God, and remember that he "gives to his beloved sleep" (Psalm 127:2).
Why did God imagine sleep? He never sleeps! He thought the idea up out of nothing. He thought it up for his earthly creatures. Why! 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. How humiliating to the self-made corporate executive that he has to give up all control and become as limp as a suckling infant every day.
Sleep is a parable that God is God and we are mere men. God handles the world quite nicely while a hemisphere sleeps. Sleep is like a broken record that comes around with the same message every day: Man is not sovereign. Man is not sovereign. Man is not sovereign. Don’t let the lesson be lost on you. 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.
John Piper, "A Brief Theology of Sleep" (1982)