Four Cups: Verses
We are constantly made aware of the importance of the four cups of wine and the obligation to drink them at the Seder. Yet no mention is made in the Torah of the four cups, nor do we recite the verses from the Torah symbolizing these four cups in our reading of the Haggadah. Why not?
The Aish Rabbi Replies:
With such a good question, you could be the Wise Son!
The four cups of wine are a rabbinical mitzvah, in commemoration of the four expressions of redemption that appear in Exodus 6:6-7: "I will take you out... I shall save you... I shall redeem you... I shall take you."
These verses refer to a promise that God made. They do not relate to the events of slavery in Egypt, nor are they verses of actual redemption. God's original promise to Abraham is spoken about in the Haggadah with "Boruch Shomer Havtachato." Thus there is no need to recite the verses of Exodus 6:6-7.
On the other hand, the Seder night mitzvot of eating matzah and telling the Exodus story have their basis in the Torah (Exodus 12:8), and are mentioned in the Haggadah.
(sources: Rashi - Pesachim 99b; Tosfot - Pesachim 108b)