Four Glasses of Wine
At the Passover Seder we drink four glasses of wine. The bouquet and the special flavor and quality of wine gives us a feeling of freedom. This is in addition to the four sons, four question and four fathers.
Part of this concept of freedom has many sub-reasons. These have been assigned to the significance of each individual glass of wine as well as all of them together. Rav Menachem Kasher of Blessed Memory in His Hagada Shelema cites more than twenty reasons for these four glasses as well for the fifth which is often called The Glass of Wine for Eliyahu Hanavi. (pg 90)
The primary source for these four reasons is a Drash on the Peusukim where G-d promises to free Benei Yisrael from slavery in four separate manners. Each number represents one of the reasons:
Say, therefore, to the Israelite people: I am the Lord. I will (1) free you from the labors of the Egyptians and (2) deliver you from their bondage. I will (3) redeem you with an outstretched arm and through extraordinary chastisements. And I will (4) take you to be My people, and I will be your God. And you shall know that I, the Lord, am your God who freed you from the labors of the Egyptians. I will (5) bring you into the land which I swore (Lit. raised My hand.) to give to Abraham, Isaac, and Jacob, and I will give it to you for a possession, I the Lord. (Shemot 6, 6-8)
Hagada Shelema citing Sefer Hamichtam says that these four different uses of the concept of freedom represent the gamut of levels of freedom. Benei Yisrael were working very hard as slaves in Egypt. (1) They would have been extremely happy to be simply relieved of these duties. This applied even if we would have remained in Egypt. (2) In addition to sparing us from the hard labor he actually freed us from slavery. (3) Furthermore, He redeemed us with an outstretched hand and utterly destroyed the oppressors. (4) Finally, he took us to be his people, which is the highest level of redemptions. Since Benei Yisrael are servants of G-d we are exempt from being slaves to other nations.
The fifth cup that many are accustomed to fill and not to drink is often called the Cup of Eliyahu Hanavi. It is a point of discussion in the Gemarah whether one is required to drink a fifth glass of wine. (Pesachim 118a) Many Talmudic discussions are left undecided. It is said that Eliyahu Hanavi will solve these problems. Perhaps that is one of the reason we leave this glass of wine.