We were slaves to Pharaoh in Egypt, and the L-rd, our G-d, took us out from there with a strong hand and with an outstretched arm. If the Holy One, blessed be He, had not taken our fathers out of Egypt, then we, our children and our children's children would have remained enslaved to Pharaoh in Egypt. Even if all of us were wise, all of us understanding, all of us knowing the Torah, we would still be obligated to discuss the exodus from Egypt (לספר ביציאת מצרים); and everyone who discusses the exodus from Egypt at length is praiseworthy.
The “maggid” section of the Haggadah is designed to fulfill the commandment of telling the story of the exodus from Egypt (סיפור יציאת מצרים). This concept is referred to in several places in the Torah, including the following verse:
"ולמען תספר באזני בנך ובן בנך את אשר התעללתי במצרים ואת אתתי אשר שמתי בם וידעתם כי אני ה'." (שמות י:ב)
“In order that you(sing.) may tell in the ear of your child and your grandchild what things I have done in Egypt, and the signs that I have done among them, that you (pl.) may know that I am the L-rd.” (Shemot 10:2)
1) Explain the change from the 2nd person singular form (תספר) to the 2nd person plural form (וידעתם) in this verse.
2) Why does the Haggadah use the phrase "לספר ביציאת מצרים" to describe the discussion of the exodus at the seder, rather than using the phrase "לספר את יציאת מצרים"
1) The change in number indicates the impact of education – that by one individual telling the story to his child or grandchild, many in the end will know and understand the meaning of the exodus from Egypt. The fact that the verb remains in the 2nd person (“you will know) rather than the third person (“they will know”) also reflects an important educational element – that in a true educational dialogue, the one who is apparently transmitting knowledge also learns and grows.
2) This usage reflects a very high level of engagement in the discussion. It is similar to the phrase "וירא בסבלותם" (“and he observed their suffering”) in Shemot 2:11. Rashi there explains that the phrase indicates Moshe’s deep involvement in the pain of the Children of Israel ("השתתפות בצער" - רש"י). It was the deep involvement of Rabbi Akiva and his colleagues in the complex discussion of the exodus that caused them to almost miss the morning prayers as described in the next passage (היו מםפרים ביציאת מצרים).