We are up to chapter 2 of Pirkei Avos, mishnah 29 (in some versions, mishnah 28). This is an important turning point, a hinge in the structure of Pirkei Avos. Until now we have dealt with Hillel and Shammai, the last of the pairs, from chapter 1 mishnah 12 onward; then with Hillel's descendants who served as Nesi'im; and at the opening of our chapter, with Rabbi Yehudah HaNasi and his son, who were also descendants of Hillel. Now the mishnah returns to Rabban Yochanan ben Zakkai.
Rabban Yochanan ben Zakkai was one of Hillel's students. The Gemara in Maseches Sukkah relates that Hillel had eighty students: the greatest of them was Yonasan ben Uziel, and the youngest of them was the Tanna before us in this mishnah, Rabban Yochanan ben Zakkai.
A leader in a time of crisis:
Rabban Yochanan ben Zakkai lived a very long life, and so did Hillel; he was therefore very young when Hillel was an old man at the end of his life. He became the leader of the Jewish people in the wake of the greatest crisis it had ever known - the destruction of the Beis HaMikdash by the Romans and the razing of Jerusalem - and he rebuilt the nation and Judaism after that devastating and bewildering event. He is the only one among the Tanna'im who is called "Rabban" without being a direct descendant of Hillel, and his appointment was something of a temporary arrangement; he is also the first, chronologically, to be called "Rabbi" in the Mishnah. This is like the beginning of a new era - the period known as the era of the Tanna'im.
He is the one who escaped from Jerusalem inside a coffin. Rabban Yochanan ben Zakkai was a moderate voice who favored making peace with the Romans and avoiding war, working within a framework that would allow them to remain the rulers - but his was not the dominant voice. When he saw that the revolt against Rome was going to be a disaster not only for Jerusalem but for the Jewish people and for Judaism as a whole, he devised the plan of slipping out through the walls of Jerusalem inside a coffin. He makes his way out and reaches Vespasian - who at that time was a general, not the emperor - who was conducting the siege of Jerusalem. Several versions of the story appear in various places in the Gemara, but in short: he is granted at least one request, and he asks for the city of Yavneh and its Sages.
In Yavneh, Rabban Yochanan ben Zakkai plants a small seed, which developed into what is called 'the vineyard at Yavneh' - so called because the Sages sat in rows, like the rows of a vineyard. There the Sanhedrin was reestablished and once again became the spiritual head of the Jewish people. He viewed his role as head of that institution and as head of the Jewish people as a temporary one, until a direct descendant of Hillel could renew the office of Nasi - namely Rabban Gamliel, Gamliel the Second, Gamliel of Yavneh.
At that time Rabban Gamliel was in hiding: his father, Rabban Shimon ben Gamliel, who served as Nasi at the time of the destruction, was one of the Ten Martyrs, and the assumption was that the Romans would seek the son's life next. It is also possible that he was young at the time. Either way, Rabban Yochanan ben Zakkai temporarily stands at the head of the Jewish people, begins the process of rebuilding after the destruction, and works out what Judaism would look like in a world without the Beis HaMikdash and without Jerusalem.
"Rabban Yochanan ben Zakkai kibel meiHillel umiShammai":
Rabban Yochanan ben Zakkai received the tradition from Hillel and from Shammai. The term "kibel" - received - returns here for a brief moment, and once again the entire transmission passes through him. Even though the previous mishnah listed those Nesi'im who were Hillel's sons, grandsons and great-grandsons, the "kibel" here returns specifically to Rabban Yochanan ben Zakkai - and he is the one mentioned as the next link in the chain after Hillel in the Rambam's introduction to the Mishneh Torah. He is the one who receives the mesorah.
The breadth of Rabban Yochanan ben Zakkai's knowledge:
He is known as a tzaddik who knew everything, a figure something like the Vilna Gaon, at this decisive moment. In two different places the Gemara describes the scope of his knowledge in the most impressive terms: they said of Rabban Yochanan ben Zakkai that he did not leave over - that he left nothing that he did not learn:
"Mikra, Mishnah v'Talmud" - the three parts of Torah: the Written Torah, the Oral Torah, and all the discussions surrounding them.
"Halachos v'Aggados" - the halachic portion and the aggadic portion.
"Dikdukei Torah v'dikdukei Sofrim" - the technical features of the text, such as matters of grammar and the like.
"Kalos v'chamuros ug'zeiros shavos" - the kal vachomer and the principles by which the Torah is expounded, and he was expert in all of them.
"Tekufos" - astronomy.
"Gematria'os" - mathematics.
The Gemara adds: what is "davar gadol" - a great thing? This refers to Maaseh Merkavah, the account of Yechezkel and his description of how he ascended to heaven, as it were, in a prophetic state in order to receive his prophecy - in other words, the realm of Kabbalah. And what is "davar katan" - a small thing? The havayos of Abaye and Rava.
Abaye and Rava belong to the second to last generation of Amoraim, and they were the teachers of those who completed the Gemara. Rava is the name mentioned most often in all of Shas, and Abaye is not far behind him. The havayos of Abaye and Rava are the central discussions of the Babylonian Talmud, and Rabban Yochanan ben Zakkai knew all of their give and take as well. It emerges that he set the standard for knowing everything. And the Gemara elsewhere, in Maseches Sotah, says of him: "batel ziv hachochmah" - the radiance of wisdom has ceased. In short, he was the complete sage who knew it all.
The Pearl in His Mouth:
Rabban Yochanan ben Zakkai used to say regularly: "Im lamadeta Torah harbeh, al tachzik tovah le'atzmecha, ki lechach notzarta" - if you have learned much Torah, do not take credit for yourself, for this is what you were created for. If a person has learned a great deal of Torah, he should not chalk it up to his own merit or congratulate himself on all his great accomplishments, since this is the very reason he was created. Fulfilling one's purpose is a good thing, but no more than that, and there is no room for grand self admiration.
The analogy worth bearing in mind is this: a person who owes his friend money and pays back his debt has no reason to congratulate himself for returning it, since by law and by right he was obligated to give the money back. It is exactly the same idea.
In the view of Rabban Yochanan ben Zakkai, a Jew - and certainly a Jewish male - was created in order to learn Torah, and the more he learns the better. And of course, it never comes to an end: there is an obligation to learn all the time, and beyond that, the Torah itself is deep and broad, with infinite breadth and depth, and one can always keep learning without ever reaching its end.
A different version is found in the Rishonim: not "im lamadeta Torah harbeh" - if you have learned much Torah, but "im asisa Torah harbeh" - if you have done much Torah. According to this version, the statement applies not only to learning Torah but also to putting it into practice - keeping the mitzvos and actually carrying them out - and for this too a person was created.
Either way, the point is that a person can never stop striving for spiritual growth, because that is why he is here. Continuing along the path is worthy of every praise, but a person should not think that he has done the Holy One, Blessed be He, any favor by doing so; he is doing it for himself. The more he is able to learn and grow, the better it is for him, since that is precisely why he was placed here: to learn and to grow.