On Shabbat we rehearse utopia, or what Judaism came later to call the messianic age. One day in seven, all hierarchies of power are suspended. There are no masters and slaves, employers and employees. Even domestic animals cannot be made to work. We are not allowed to exercise control over other forms of life, or even forces of nature. On Shabbat, within the covenental society, all are equal and all are free. It is the supreme antithesis of Egypt. What a stroke of genius it was to introduce a foretaste of the future into the present, to remind us constantly of our ultimate destination and to be strengthened by it regularly on the way.
So Exodus ends as Genesis began, with the holy day on which God and His image, humankind, find rest at the still point of the turning world, in the midst of the otherwise restless strife of the human condition. The Israelites were called on to be among the nations what Shabbat is in the midst of time — a sign of what ought to be, in the midst of what actually is.
Rabbi Jonathan Sacks, Covenant & Conversation: Exodus