There are numerous explanations as to why we use THREE matzot at the Seder. Kohen, Levi, and Yisrael - Avraham, Yitzchak, and Yaakov. What does that have to do with anything? All three of the Avot were directly involved in the story of the Exodus! Avraham was the original person Hashem told about this. While Hashem originally says it will be for a period of 400, Hashem starts the year from the birth of Yitzchak. Finally, we know that it is Yaakov and his sons going down to Egypt that was the first step in the beginning of the Exile. All three Avot are connected to the story of the Exodus.


haggadah Section: Yachatz