The Cup of Elijah
"According to ancient Jewish tradition, the prophet Elijah did not die; he simply ascended to heaven in a fiery chariot and vanished. The belief grew that someday Elijah would return to earth, and as the forerunner of the Messiah he would prepare the way for a great Age of Peace.
Since Passover, the Festival of Freedom, expresses hope in the eventual redemption of mankind and its deliverance from all evil, who could be a more welcome guest at the Seder than Elijah? And so, in every Jewish home a special cup is reserved for the prophet Elijah, the guest of honor."
(The Concise Family Seder. Prepared by Rabbi Alfred J. Kolatch. Jonathan David Publishers, Inc. Middle Village, New York. 1987 by Alfred J. Kolatch)