In addition to the four cups of wine that each participant drinks during the Pesach Seder, a fifth cup is placed on the Seder table. This cup, which is not drunk, is known as Kos Shel Eliyahu, Eliyahu’s Cup.

Regarding this cup, the Alter Rebbe states in his Shulchan Aruch:1 “It is customary in these countries to pour an additional cup — one more than for those seated. This cup is called Kos Shel Eliyahu.”

What is the reason for this additional cup, and why is it so named?

There is a difference of opinion in the Gemara2 regarding the necessity of drinking a fifth cup of wine. Since this matter was not clearly adjudicated, there are those who say3 that a fifth cup is poured and placed on the table, but not drunk. This cup, they say, is called Kos Shel Eliyahu, because, as Eliyahu will clarify all doubtful halachic matters, he will clarify the ruling about this cup as well.

However, from Chok Yaakov4 and the Alter Rebbes Shulchan Aruch5 it is clear that the fifth cup and Kos Shel Eliyahu are two distinct entities, each involving different rulings as to whether it need be poured at all, whether the wine may be drunk, and whether it is poured for each individual in attendance or only once for all those assembled.

The question thus remains: What is the reason for the custom — not mentioned at all in the Gemara or the Rishonim — of placing an extra cup of wine on the table, a cup which is not drunk, and calling it Kos Shel Eliyahu?

The very fact that Kos Shel Eliyahu is merely placed on the table and not consumed indicates that it is bound up with a level of Divine service that is loftier than man’s service of performing the ritual of drinking the four cups of wine. This is so, for Kos Shel Eliyahu is bound up with the final Redemption, something that transcends man’s service.

The fact that Kos Shel Eliyahu and the ultimate Redemption are intimately linked can be deduced from the fact that the Alter Rebbe elucidates the custom of Kos Shel Eliyahu after first stating the following:

“In some places, it is the custom on the [first] night of Pesach to leave the bedroom doors unlocked, for it is a propitious night for the Jewish people unto all generations to be redeemed from this exile. For if Eliyahu (who will bring the tidings of Redemption) comes, he will find an open door, and we will go out and greet him speedily. We firmly believe this, and in so believing, there is great reward.”

The Alter Rebbe then goes on to state: “And it is customary in these countries to pour... Kos Shel Eliyahu.” Clearly then, the Kos Shel Eliyahu is bound up to the Jews’ faith in the coming Redemption.

This belief is to be found within all Jews, for all are “believers and children of believers.” And this is so, regardless of the individual’s revealed level of service. For every Jew intrinsically believes in and awaits the coming of Mashiach — this belief and anticipation being a Divine command both in the Written and Oral Torah.6 Moreover, these feelings grow ever stronger as we move closer to the Redemption.

This is why it is specifically in these later generations, when the time for the final Redemption draws closer and the passionate longing for its coming grows stronger, that the custom of pouring a Kos Shel Eliyahu has become widespread.

Also, the expression “to pour an additional cup — one more than for those seated,”alludes to the fact that Eliyahu becomes one of those who are seated at the Seder table.

For the belief of the Jewish people on this night — the night when G‑d revealed Himself in His full glory, and which finds physical expression in the cup and the wine — is in itself sufficient to unite Eliyahu with the partakers of the Seder, to the degree that Eliyahuhimself becomes a Seder participant.

Based on Likkutei Sichos, Vol. XXVII, pp. 52-55.