On the first two nights of Passover, during the Passover Seder, there are several laws that the Torah commands us to observe, both biblical and rabbinic. For example, we must eat Matzah, whose conceptual meaning is that, being "Bread of Affliction," unleavened bread without taste, Matzah symbolizes unquestioning devotion to the observance of Torah and Mitzvot. Generally, intellect is represented by taste, while devotion is represented by the lack of taste. In other words, fulfilling Mitzvot because God commands it, not based on any rational conclusion.
Another example of the laws of the Passover Seder is the four cups of wine. Our sages instituted that, throughout the reading of the Haggadah, we drink four cups of wine to remember the four expressions of redemption that the Torah uses in the story of the Exodus (see Exodus 6:6-7): "I will bring them out," "I will save them," "I will redeem them," and "I will take them.".
In 1906, the fifth Rebbe of Chabad, Rabbi Shalom DovBer (1860-1920), revealed to the public an ancient custom dating back to the time of the Baal Shem Tov, the founder of the Hasidic movement. The Baal Shem Tov used to prepare a meal on the last day of Passover, consisting of matzah and four cups of wine, which he called "The Meal of the Messiah" (Seudat Mashiach). The connection between this time of year and the Messiah is that the reading of the prophets following the Torah reading mentions the coming of the Messiah.
Now, the concept of wine in the Torah represents understanding and pleasure: just as wine has a very particular taste (in contrast to water which is tasteless), understanding a matter generates a particular "taste" and pleasure for the person in what they understood.
Based on this idea, we must understand why we drink four cups of wine (representing understanding) at the Passover Seder, whose central point is eating matzah, which represents the nullification of understanding. Furthermore, what is the difference between the matzah and the four cups of wine at the Passover Seder and those at the Sedat Mashiach?
The idea, in short, is this: on the first night of Passover, the focus is on Matzah, which, as mentioned, represents self-annihilation (bitul, in Hebrew), while the wine symbolizes that this annihilation must also be incorporated into the intellect—that is, coming to understand how the correct attitude toward life is to be surrendered to the Divine Will. Perhaps we could even say that this is why the wine recalls the four expressions of redemption: we must not only close our eyes and observe the Torah, but we must come to understand how the different aspects of life are modified, improved, and refined through the Torah. It is not enough, so to speak, to remember that God brought us out of Egypt; we must understand how He did it.
On the other hand, the emphasis in Seudat Mashiach is on wine, because in the time of the Messiah, "The earth will be filled with the understanding of God, as the water covers the sea" (Isaiah 11:9): the whole world will see and understand God. However, we also eat Mazta, because we must always remember that there are higher levels of understanding and drawing closer to God, even during the time of the Messiah.
May God bless us with the greatest blessing of all, the speedy coming of Messiah, to celebrate the last days of Passover in Jerusalem, Amen.
Pesaj kosher veSameaj!