From Tim Keller's article, "Wisdom and Sabbath Rest," which is adapted from a 2007 leadership training session talk at Redeemer.
The purpose of Sabbath is not simply to rejuvenate yourself in order to do more production, nor is it the pursuit of pleasure. The purpose of Sabbath is to enjoy your God, life in general, what you have accomplished in the world through his help, and the freedom you have in the gospel—the freedom from slavery toany material object or human expectation. The Sabbath is a sign of the hope that we have in the world to come.