Very simple and straightforward?
Actually, full of problems.
Why not say, “Whoever does not eat three things on Pesach has not done their duty”?
Is it because we already know that we must eat pesach, matzah and maror and hardly need a reminder? One can not imagine Rabban Gamli’el merely reiterating something so obvious.
But the Torah command does not equate the three foods as Rabban Gamli’el does. It has an order of priorities. Pesach (the paschal lamb) comes first, even before matzah, and maror appears as an accompaniment.
What Rabban Gamli’el does is to make an amazing contribution to the reshaping of Judaism.
He raises the status of the matzah and maror because by his time the Temple has been destroyed and it is no longer possible to carry out the Passover sacrifice. Shall the Pesach observances be abandoned as a result? Christianity gave one answer; Judaism, thanks to Rabban Gamli’el, constructed a different one.
For Christianity, the paschal sacrifice was no longer necessary and the Seder could move into limbo because Jesus was the paschal lamb and his death replaced the sacrifice.
What did Rabban Gamli’el say? There are three requirements, not one: pesach, matzah and maror, and when pesach is not practicable, the other two move up in status.
When the Temple is rebuilt, the paschal offering will return; in the meantime we talk about it and place a reminder on the table without eating it.
This is already an important development, but Rabban Gamli’el makes a second crucial contribution by saying, “Don’t only eat the required foods but speak about them”.
Seder is a time for eating, but also for explaining. Isn’t this the great mitzvah of Pesach: v’higgadeta l’vin’cha (Ex. 13:8)?
Isn’t it what lies behind the story of the five rabbis in Bnei Brak, which shows that even the greatest of the sages can keep talking about the Pesach themes all night?
Isn’t it also what lies behind the passage about the four sons, to whom the story must be told in ways that fit their various degrees of understanding?
The duty to speak about the Exodus long pre-dated Rabban Gamli’el, but he turned it into a ritual.
Rabban Gamli’el is one of the moulders of the Pharisaic tradition which in its turn moulded the Judaism we practise today.
The Haggadah is a Pharisaic construction, built upon foundations laid in the Torah. The Pharisees‘ principle is expressed in Pir’kei Avot (3:3), which tells us that when we eat we must talk Torah, and only then does it become “the table of the Lord”. If this applies to any meal, all the more does it apply to the Seder.
The Greeks developed the idea of the meal-table symposium where there was food and drink – and talk and debate. Characteristically, one of Plato’s works is called “Symposium”. For the Greeks, the table became a philosophical meeting place.
Rabban Gamli’el and the Jews also turned the table into a cultural experience, but more: they made it “the table of the Lord”; there was philosophy, but spirituality too.
What Rabban Gamli’el is telling us is to eat and drink and also reflect on the miracles of the Exodus and the hope for messianic redemption.