The Sages instituted that on Seder night one drinks four cups of wine. Why?

From where is the obligation to drink four cups on Passover derived? Rabbi Yohanan says in the name of Rabbi Benaya: The four cups correspond to four expressions of redemption: “Therefore, say to the children of Israel: I am the Lord and I will take you out from under the burdens of Egypt and I will deliver you from their work and I will redeem you with an outstretched arm and with great punishments” (Exodus 6:6). The four expressions are: “I will take you out,” I will deliver you,” “I will redeem you,” and “I will take you” (Exodus 13:15).

Rabbi Levi says: The four cups correspond to the four kingdoms that subjugated Israel.

The Rabbis say: The four cups correspond to the four cups of retribution that the Holy One, blessed be He, is destined to have the nations of the world drink…and corresponding to them the Holy One, blessed be He, will have Israel drink four cups of consolation. (Jerusalem Talmud, Pesaĥim 10:1)