Seder night I am praying to G-d for the first time. A slave is incapable of experiencing something the first time it happens. You know there am people who meet you for the first time, and they look at you and they think they know all about you. Here I want you to know the saddest thing between parents and children is that parents always know how to look at their children for the second time. Can you imagine what a privilege Seder night is - something happens and I am looking at my children for the first time.
Nobody is a bigger expert on the first time than children.
They know the secret of the first time. Because on Pesach, when I see G-d for the first time, I see people for the first time. Until Pesach came I didn't invite poor people to my house because I was accustomed to seeing them on the street. If I would only see them for the first time, I couldn't be able to stop myself from inviting them to my house. So, Seder night, everything is for the first time.