The Exodus from Egypt should be included at night. Rabbi El'azar ben-Azaryah said, "I am like a seventy-year-old and have not been able to explain why the Exodus from Egypt is to be recited at night, until ben-Zoma based it on the following midrash: The Torah says, 'So that you will recall the day you left Egypt all the days of your life' [Deuteronomy 16:3]; [if it had only said] 'the days of your life' this would have indicated the daytime, 'all the days of your life' must include the nightime. The rest of the sages [give a different midrash to this verse]: 'The days of your life' indicates this present world, 'all the days of your life' includes the Messianic Age.
6:
The statement of Rabbi El'azar ben-Azaryah that he is "like a seventy-year-old" refers to one of the most dramatic episodes in the history of the development of the Oral Torah in the second half of the first century CE. After the death of the first Hillel (around 20 CE) the presidency of the Sanhedrin was vested in his descendants. He was followed by his son, Rabban Gamli'el and by his grandson Shim'on (who died during the Great War against the Romans). During the decade immediately after the way (70 – 80 CE) the leadership was vested in Rabban Yoĥanan ben-Zakkai, the undisputed leader of the school of Hillel even though he was not a descendent of Hillel. After his death, however, the presidency reverted back to Hillel's heir, his great-grandson, also called Gamli'el. These were difficult years for the Jewish people. The nation had been defeated and subjugated by the Romans, the Bet Mikdash and its panoply destroyed forever, and the sages, assembled in the little town of Yavneh, locked in a struggle as to which 'version' of Pharisaic Judaism would become predominant – the liberal school of Hillel or the conservative school of Shammai.
7:
Rabban Gamli'el ("of Yavneh", to distinguish him from his grandfather "old" Rabban Gamli'el) did his best to create and preserve unity in these trying circumstances. On a couple of occasions previously he had "brought to heel" the most prominent, respected and loved of all the sages of the school of Hillel, Rabbi Yehoshu'a (ben-Ĥananyah). Rabbi Yehoshu'a in his youth had been one of the two students who smuggled Rabban Yoĥanan ben-Zakkai out of beleaguered Jerusalem, and now in his old age he was the most popular and respected figure at Yavneh. (Later on Rabban Gamli'el was also to face down Rabbi Eli'ezer [ben-Hyrcanos], Joshua's dear friend and rival, of the school of Shammai.) A young student (later to become very famous in his own right, Rabbi Shim'on ben-Yoĥai) caused the explosion by asking whether the Evening Service was compulsory or voluntary. Rabban Gamli'el forced a showdown in the full plenum, haughtily subjected Rabbi Yehoshu'a (who held a different view) to a humiliating 'recantation'. The assembled sages exploded and voted to depose Rabban Gamli'el from the presidency of the Sanhedrin.
8:
The problem now was who to elect as his replacement. The most obvious candidate was Rabbi Yehoshu'a, but he could not be chosen because he was too 'interested' a party. The choice fell on a young scholar, Rabbi El'azar ben-Azaryah, of priestly stock, financially well-off and with no real enemies or rivals. On being offered the presidency El'azar said what would be considered today the most PC thing he could say: "I must discuss this with my wife first". She was against the whole idea, since she could easily see that he had been chosen not for his own merits but as a further punishment to Rabban Gamli'el. She pointed out that in all probability they will all make peace again very soon and Rabban Gamli'el will be restored to his hereditary position: "What will then become of you?" His youthful reply was that it was better to hold that honour even only for one day than never to have held it at all! His wife then pointed out that he was very young (which was probably why he was chosen – to rub salt into the wounds of Rabban Gamli'el, as it were). He was only eighteen, says the Gemara, thus he was now able to say "I am like a seventy-year-old" – replacing the aged Rabban Gamli'el. (The Gemara gives a 'miraculous' explanation of his sudden aging; I prefer the more prosaic one I have offered.)
9:
Thus Rabbi El'azar ben-Azaryah, in our mishnah is in fact saying that although I have become, overnight as it were, a seventy-year-old, nevertheless there are still many points of halakhah that I do not fully understand, and one of them is how we justify reciting Parashat Tzitzit of the Shema at night; but now Rabbi Shim'on ben-Zoma has 'explained' it to me.
10:
The end of the episode. Rabban Gamli'el and Rabbi Yehoshu'a were reconciled and Rabban Gamli'el, appropriately chastened, was restored to the Presidency of the Sanhedrin. However, he had to accept Rabbi El'azar ben-Azaryah as his junior partner in the presidency.