כוס של אליהו
Why is it called Elijah's Cup?
In the Talmudic literature, Eliyahu Hanovi would visit rabbis to help solve particularly difficult legal problems. Malachi had cited Elijah as the harbinger of the eschaton. Thus, when confronted with reconciling impossibly conflicting laws or rituals, the rabbis would set aside any decision
until Elijah comes.
One such decision was whether the Passover-Seder required four or five cups of wine. Each serving of wine corresponds to one of the
four expressions of redemption in the Book of Exodus:
I am the Lord, and I will bring you out from under the burdens of the Egyptians, and I will deliver you from their bondage, and I will redeem you with an out-stretched arm and with great acts of judgment, and I will take you for my people, and I will be your God; and you shall know that I am the Lord your God, who has brought you out from under the burdens of the Egyptians(Exodus 6:6-7).
The next verse,
And I will bring you into the land which I swore to give to Abraham, to Isaac, and to Jacob; I will give it to you for a possession. I am the Lord. (Exodus 6:8) was not fulfilled until the generation following the Passover story, and the rabbis could not decide whether this verse counted as part of the Passover celebration (thus deserving of another serving of wine). Thus, a cup was left for the arrival of Elijah.
In practice, the fifth cup has come to be seen as a celebration of future redemption. Today, a place is reserved at the seder table and a cup of wine is placed there for Elijah. During the seder, the door of the house is opened and Elijah is invited in. Traditionally, the cup is viewed as Elijah’s and is used for no other purpose.