Why Four Cups of Wine at the Seder?
During the Passover Seder we drink four cups of wine. The Jerusalem Talmud cites several sources for this requirement.
The first source, and the most frequently cited for drinking four cups of wine at the Seder is in this week’s parsha, when G‑d sends Moses to liberate the Jews from Egyptian bondage. In his charge to Moses G‑d says:
          …I shall take you out from under the burdens of Egypt.
          I shall rescue you from their service
          I shall redeem you with an outstretched arm and with great judgments.
I shall take you to Me for a people and I shall be a G‑d to you…
It was based on these four expressions of liberation that our Sages instituted drinking four cups of wine at the Seder Pesach night.
Four Cups In the Butler’s Dream
The Jerusalem Talmud, cites an earlier Biblical source (Genesis 40:11-13), where the Torah recounts Pharaoh’s butler’s dream and Joseph’s interpretation of it, in which the word kos-cup appears four times:
“Pharaoh’s cup was in my hand, and I took the grapes and squeezed them into Pharaoh’s cup. I placed the cup on Pharaoh’s palm…
“In another three days, Pharaoh will count your head, and restore you to your position. Then, you will place Pharaoh’s cup into his hand…”
The four references to cups here also allude to the four cups that we drink at the Seder.
We must try to understand how the references to Pharaoh’s cup relate to the liberation of the Jewish people centuries later.
Moreover, upon deeper reflection it would appear that this dream with its four cups relates more to exile and bondage than to anything else.
First, it was a dream. It has been pointed out on many occasions that a dream is a metaphor for exile in which reality is obscured and contradictions abound.
Second, it was the dream of Pharaoh’s butler. Pharaoh is the very symbol of exile.
Third, the butler himself epitomized Galus. It is he who “did not remember Joseph and he forgot him.” His double amnesia is another metaphor for exile in which we forget who we are and where we are going.
Fourth, when the butler finally remembered Joseph because Pharaoh’s dream needed to be interpreted, he describes Joseph in unflattering terms. The butler was not interested in promoting Joseph but did everything in his power to diminish Joseph’s stature and influence even as the butler was compelled to mention Joseph’s name to Pharaoh.
Fifth, the dream itself is about providing wine – a symbol of joy – for Pharaoh the leader of Egypt and prime symbol of Egyptian bondage (which either he or his successor initiated, depending on the two views cited by Rashi as to the meaning of “a new king arose who did not know Joseph”). At any rate, giving Pharaoh wine on his birthday — the day our Sages say one’s mazal-power is dominant — suggests providing the forces of exile with greater vitality, joy and dominance.
These components of the butler narrative can hardly be an allusion to the theme of Passover night when we celebrate the Exodus! How in the world would our Sages identify the four Seder cups with the butler’s dream?
Exile, Redemption and Pharaoh’s Dream
The answer to this question lies in a better understanding of the process of exile and Redemption. This novel approach contradicts the superficial understanding that exile and Redemption are two contradictory periods; where one ends the other begins but never the twain shall meet. This is indeed the way it appears and feels. In truth, however, Redemption itself is embedded within exile. Redemption is “merely” the dynamic force that reveals the true nature of exile.
This idea has its roots in Pharaoh’s twin dreams which catapulted Joseph to his position of power in Egypt, second only to Pharaoh.
In his dreams, Pharaoh sees seven fat cows, and good ears of grain, which are swallowed up by seven meager cows and thin ears of grain, without improving their impoverished forms.
As we know so well, Joseph interpreted these dreams as a forecast of seven years of plenty to be swallowed up and forgotten by seven years of famine.
Without being asked for his advice, Joseph told Pharaoh to store grain in the seven years of plenty to avert a catastrophe in the seven years of famine.
Pharaoh was so impressed with this interpretation and advice that he instantly promoted Joseph, a lowly foreigner-slave-prisoner, to the penultimate position of power in the land.
There are three obvious questions here: First, what was so brilliant about interpreting a dream about food sources disappearing as an allusion to seven years of famine to follow seven years of plenty?
Second, why couldn’t Pharaoh’s wise men think of this rather obvious interpretation?
And thirdly, commentators ask whether Joseph’s unsolicited advice was a dangerous form of hubris? Yet Pharaoh did not chastise him for offering advice without being asked.
Joseph’s Brilliance
The Rebbe answers all three questions by referring to a part of the dream that nobody other than Joseph could decipher. There is a point in time during Pharaoh’s dream when the fat cows and the lean cows stand together on the Nile. Pharaoh’s advisors could not understand how, if these two sets of cows represent plenty and famine, could they co-exist?
Joseph’s brilliance was that he was able to detect in this aspect of the dream the very solution to the problem of famine predicted by the dream. By storing food in the seven years of plenty in anticipation of seven years of total famine and, conversely, by eating the food from the seven years of plenty in the seven years of famine, it was possible to see that both of these phases could exist simultaneously. While the Egyptians enjoyed the bountiful harvests in the seven years of plenty they were living with knowledge of the impending famine and feverishly storing away food.  While they were living during the seven years of famine, they were able to enjoy the bountiful yield of the seven years of plenty.
Joseph was not offering unsolicited advice. Rather, he saw that the proper interpretation of the dream carried within it the solution to the problem that the dream foreshadowed.
The Secret of Galus
The Rebbe applies this to the very concept of a dream, and the inner dynamic of exile, which a dream symbolizes.
Any dream that combines opposites is rooted in a spiritual dynamic which transcends the conventional order of existence. Any force that can combine opposites must, by definition, transcend them. Pharaoh’s dream illustrated this notion because, as Joseph demonstrated, it incorporated bringing opposites together; seven years of plenty and seven years of famine.
Moreover, Joseph’s deciphering of the dream revealed that it contained the seeds for its deciphering which would resolve the apparent contradictions, and, in a most down-to-earth fashion, provide for deliverance from the impending disaster.
Similarly, the Rebbe explains, Galus-exile contains within it the most powerful energies that can also combine opposites. The power to extricate ourselves from it is embedded within Galus itself. The entire process of Redemption is thus not one of negating and destroying exile but, on the contrary, revealing its true spiritual and transcendent nature.  
Four Cups and the Butler’s Dream Revisited
While focusing our thoughts on Redemption, we can now understand how the source of drinking four cups of wine at the Seder can be derived from the dream of Pharaoh’s butler. This is possible even considering the fact that everything surrounding Pharaoh, the butler and the dream reeks of exile in its most blatant form!
However, in light of the Rebbe’s analysis of Pharaoh’s dreams and Joseph’s interpretation of them, we can also understand the relationship of the butler’s dream to Redemption. Precisely because Redemption is not the simple negation of exile, it reveals its underlying and essential nature. In every aspect of the butler’s dream lie the seeds of Redemption.
So, when we sit at the Seder table in the days of our exile and drink the four cups of wine we are, in effect, deciphering the butler’s dream ourselves and revealing its true power. In exile we see the dynamic of Redemption.
Emphasis on Four Expressions of Redemption
Now that we have explained how the cups in the butler’s dream relate to the Exodus, we must ask why the Alter Rebbe, in his Shulchan Aruch (Code of Law), cites the reason for the four cups of wine as the four expressions of liberation that appear in this week’s parsha? Why not cite the reference to the four cups of Pharaoh in the butler’s dream?
To answer this question, we have to ask what practical difference there is between the reason that it is a reminder of the four cups of Pharaoh or the four expressions of redemption?  Don’t they both convey the message of Redemption?
The answer is that when we are deeply in exile, we have to work hard to see the redemptive element embedded within exile. When however, we are close to the actual Redemption, the focus is more on the Redemption itself and not on discovering the seeds of Redemption embedded in exile.
The Alter Rebbe, the founder of Chassidus Chabad, pioneered the dissemination of the teachings of the Ba’al Shem Tov, which are the foretaste of the teachings of Moshiach. Therefore, as we enter the final thrust towards, and preparation for, the final Redemption, it becomes crucial to focus on the dynamic of Redemption and to only secondarily discover the seeds of Redemption implanted in exile.  So, while we should endeavor to see the seeds of Redemption even when we experience exile, our emphasis now should be on the actual Redemption!