No Virginia, Elijah doesnt really visit every seder
On page 118a of the standard edition of Tractate Pesachim of the Babylonian Talmud, we find the statement that Rabbi Tarfon used to recite the Hallel Psalms over the fourth cup of wine. However, in many manuscript editions of this text, it is the fifth cup of wine. The seder, it turns out, is built around a series of text recitations. We fill a cup of wine at the beginning of each, and drink it at the end: 1) Kiddush (the blessing over the holiday); 2) Magid (the central midrash of the Haggadah); 3) Birkat Hamazon (the blessing after the meal); and 4) the Hallel Psalms. As the medieval commentators tried to understand the discrepancy between the two versions of Rabbi Tarfons teaching, it became clear that the dispute is over whether the Hallel of the Haggadah is just one text section, or whether it should be seen as two separate parts. This dispute was never resolved, so the compromise solution was to pour a fifth cup but not to drink it. Thats why we fill a fifth cup (one for the whole table) near the end of the seder.
Meanwhile, back in the Bible, Elijah, who features in the Book of Kings as a rather wild and wooly prophet, telling off kings (I Kings 21), dueling with pagan prophets (I Kings 18), and meeting God in a still small voice at Mount Sinai (I Kings 19), achieves the distinction of being one of the only two people in the Bible who does not die, but who ascends to heaven directly (II Kings 2); the other was Enoch (Genesis 5:21-23). Perhaps this tradition gave rise to another one, that appears as the last verse of the last book of the Prophets, Malachi 3:23-24:
Lo, I will send the prophet Elijah to you before the coming of the awesome, fearful day of the Lord. He shall reconcile parents with children and children with their parents, so that when I come, I do not strike the whole land with utter destruction.
Based on his presumed eternal presence, and on these verses, Elijah became the forerunner of the messiah, the proclaimer of redemption. This image of him permeates our tradition, popping up in the liturgy and in folk tales. It even appears in the New Testament, when Jesus suggests that John the Baptist (whose role is to proclaim the coming redemption) is actually Elijah (Matthew 11:14). One of the tasks Elijah is expected to perform is to solve all unresolved halachic arguments, so that redemption can come. When agreement cannot be reached in the Talmud, the word teiku closes the discussion (this is used in modern Hebrew to mean a tied score in a game). Traditionally, this is understood as an abbreviation for tishbi yitaretz kushiot uvaayot, meaning Elijah will resolve all questions and problems.
The fifth glass at the seder, therefore, awaits Elijahs coming, so that we will know once and for all if we are required to drink it. Hence Elijahs cup. So no, he doesnt visit but how we wish that he would! On this feast of redemption, how we long for redemption!
But wait, theres more: in Exodus 6:6-7 we find:
I will free you from the labors of the Egyptians and deliver you from their bondage. I will redeem you with an outstretched arm and through extraordinary chastisements. And I will take you to be My people
Traditionally, the four expressions for Gods redemption of Israel: free, deliver, redeem, and take, are associated with the four cups of wine. The debate arises over the next verse: I will bring you into the land Is bringing us to Eretz Yisrael part of our redemption, or something else? Should we drink a fifth cup to it, or hold at four? Is getting out of slavery the whole deal, or is becoming sovereign in our own land the ultimate fulfillment of the redemption?
Dont ask me! But if Elijah should stop by your seder to reconcile parents with children and children with their parents (thus indeed bringing the redemption a few minutes closer), be sure to ask him.