[Background: We are discussing the Three Oaths according to Rabbi Zeira, whom the halacha follows. According to this view, the Oaths apply only to the Jewish people as a whole. In Siman 10, the Rebbe asked a basic question: does the oath against "going up as a wall" prohibit only military invasion, or even peaceful immigration with the permission of the ruling power? Now the Rebbe will quote the Ramban in support of the second possibility.]
The Ramban in Maamar Hageulah, end of Shaar 1, writes:
Now, after this redemption which took place with the permission of Cyrus, you know from Megillas Esther the great dispersion and tremendous scattering that was the condition of our people in all the provinces of King Achashverosh, from India to Ethiopia. And even after that, they did not ascend to Eretz Yisroel. Only a few came with Ezra from Babylonia... In my opinion, it is possible that Cyrus's permission was only for the kingdom of Yehuda. And even if you argue that his permission was for everyone, as the verse says "throughout his kingdom" (Ezra 1:1), the other tribes did not want to ascend, for they did not wish to force the end, since it was known to them that the promise of remembrance after 70 years was said to Babylonia, not to them.
So you see clearly that although the immigration at that time was done with the government's permission, and although it was a Heavenly remembrance, to go up to Eretz Yisroel and build the Temple, and it was after the end-time of 70 years written in Scripture, and despite the fact that there were prophets at the time (Chagai and Zechariah) who prophesied that this was a Heavenly remembrance and that the Jewish people should ascend - still the Jews in all the provinces were afraid to ascend, lest they force the end, since the prophecy was said about Babylonia, not they.
One might ask: why does the Ramban mention the oath not to force the end, rather than the oath not to go up as a wall? Doesn't any mass immigration violate the oath not to go up as a wall, according to what we are saying now? The answer is that all the oaths in Shir Hashiriim are said in the same language: "Do not arouse and do not awaken the love until it is desired." The Sages understood that the time when "it is desired" is the time of the End, the redemption and the coming of the messiah. The oath is written three times to indicate three oaths covering three different situations, sufficiently different that we would not have been able to deduce one from the other, had they not all been written. However, now that Scripture has revealed them all to us, we understand that all three oaths were made for one reason - so that we should not end the exile prematurely.
But this Ramban seems to directly contradict the Gemara in Yoma 9b (mentioned above in Siman 10). There Reish Lakish criticized the Babylonian Jews and said that if they had all come up together as a wall in the time of Ezra, the Divine Presence would have rested on the Second Temple. And the Midrash goes even further and says that the Temple would never have been destroyed. This shows that their decision not to come was a sin - not as the Ramban says.
We can reconcile this in three ways:
1) Rabbi Yochanan disagrees with Reish Lakish and says, "Even if they had all come up in the time of Ezra, the Divine Presence would not have rested on the Second Temple, for the Torah says: G-d will beautify Yefes, but He will dwell only in the tents of Shem (Bereishis 9:). This means that although the Persians, who are descended from Yefes, would fund the building of a beautiful Second Temple, the Divine Presence would rest only on the First Temple, which was built by Solomon, a descendent of Shem."
2) Reish Lakish was criticizing only the Jews of the province of Babylonia itself who failed to heed Ezra's call, but the Jews of the other 126 provinces acted correctly, as the Ramban says.
3) Most likely of all, Reish Lakish was not criticizing the Babylonian Jews for the sin of not coming to Eretz Yisroel, but rather for other sins they had committed for which Hashem punished them by not allowing them to come to Eretz Yisroel. In a similar vein, the Gemara says (Berachos 4a) that the Jews of Ezra's time really should have entered Eretz Yisroel in a miraculous way as in the time of Yehoshua, but their sins prevented it. One might ask: why then did the Divine Presence not rest on the Second Temple? It was not the Jews fault that they didn't come up - they weren't permitted to do so! The answer is that it was still indirectly their fault, since it was their sins that caused it. We find the same idea in the case of Moshe Rabbeinu in Erechin 32b: Moshe did not ask Hashem to take away the inclination toward idol worship because he did not possess the merit of Eretz Yisroel and his prayer would not have been effective. We see here that Moshe lacked the merit of Eretz Yisroel, despite the fact that he wanted to enter so badly and prayed many times that Hashem should annul HIs decree and allow him to enter - because indirectly, it was his fault, since his sin was the cause of that decree.
The Pnei Yehoshua on Kesubos goes a step further than the Ramban. He asks why Rav Yehuda based his prohibition on moving to Eretz Yisroel on the verse, "To Babylonia they shall be brought" if in the end his prohibition rests on the oaths in Shir Hashirim (the same question with which Vayoel Moshe begins in Siman 1). Furthermore, this verse was written at the time of the destruction of the First Temple, when the Jews were exiled to Babylonia. So why is it relevant to the second exile, when they were exiled by Rome and went to other lands? His answer is that aside from the small number who came up with Ezra, the Jewish people never left Babylonia. They held that the oath applied even to the Jews of Babylonia (unlike the Ramban, who only says it applied to the Jews in the other provinces), even when the 70 years of exile expired. The Divine remembrance that was manifested in Darius's permission for the Jews to return was merely a small comforting gesture, not the real redemption. So when the second exile began, the Jews of Babylonia were still in their places from the first exile, so the verse, "To Babylonia they shall be brought" still applied to them. How does this fit with Reish Lakish in Yoma 9b, who criticized the Jews for not returning with Ezra? It doesn't, says the Pnei Yehoshua. Reish Lakish disagrees with the Gemara in Kesubos.
[Some Zionists have claimed that the Pnei Yehoshua says that Reish Lakish disagrees with the entire law of the Three Oaths. See Rabbi Shlomo Aviner, reason number 9. Actually, all he says is that the Gemara in Kesubos holds that the Oaths applied even to Ezra's time, and Reish Lakish disagrees with that. Reish Lakish held that Ezra's return was meant to be a redemption for the entire Jewish people and so the oaths did not apply then. But certainly they apply during exile.
Rabbi Yaakov Zisberg in his Nefesh Adah claims that the Ramban is irrelevant to today because the Jews at the time of Ezra must have been warned specifically by the prophets that the redemption was only for those in Babylonia, not those in other provinces. We today have no prophecy so this is not a problem. He misses the point that on the contrary, today we have no prophet at all to tell us when exile ends, so there is no way any Jews from any part of the world can end it on their own. It is forbidden unless we are notified otherwise.]
The words of the Ramban and Pnei Yehoshua make sense, because it would be hard to believe that the Jews of that time refused, on the whole, to heed Ezra's call. Certainly, had he told them that they were obligated to ascend, and that the Divine presence resting on the Second Temple depended on their coming, they would not have disobeyed. And on the contrary, we find that Ezra actually made sure certain Jews stayed in Babylonia. The Gemara in Kiddushin 69b says, "Ezra did not ascend from Babylonia until he made it like fine flour," meaning that he made sure to leave the Jews with the best lineage there.
Besides, we find that there was a chain of Torah scholarship in Babylonia throughout the Second Temple period. For example, Hillel the Elder, whose school of learning eventually became definitive in establishing halacha, originally lived in Babylonia, as we see from the Gemara in Pesachim 66a. The Gemara tells how once, Erev Pesach fell on Shabbos and no one knew if it was allowed to slaughter the korban pesach - not even the Bnei Beseira, the Nesi'im - leaders of the Sanhedrin. "There is one man who came up from Babylonia," people informed the Bnei Beseira, "and his name is Hillel the Babylonian, and he studied under the two greatest sages of the generation, Shmayah and Avtalyon, and he knows whether the korban pesach supercedes Shabbos or not." Hillel said that the korban pesach could indeed be slaughtered, and the Bnei Beseira promptly stepped down and appointed Hillel as the Nasi instead. From the reference to Hillel as "one man who came up from Babylonia" it seems that Hillel lived in Babylonia and had just come to Jerusalem to take part in the korban pesach. Only after he was appointed Nasi of the Sanhedrin was he obliged to move permanently to Jerusalem, but until then, he spent all his life in Babylonia.
The Maharsha even says that Hillel did not usually come to Jerusalem for Pesach or other festivals. The Gemara relates that Hillel chided the Bnei Beseira, "What caused me to come up and become Nasi over you? Your laziness in not studying under the two greatest sages of the generation, Shmayah and Avtalyon." The Maharsha explains, "What caused Hashem to put the idea into my mind to come from Babylonia to Jerusalem just for this Pesach, which happened to fall on Shabbos?" And of course, we see that Hillel was living in Babylonia up till that point. And so is indicated in the language of the Gemara, "There is one man who came up from Babylonia" and in the fact that he was nicknamed "Hillel the Babylonia".
However, the question remains: if he lived in Babylonia, how did study under Shmayah and Avtalyon, as the Gemara in Pesachim says he did? There is even a famous story about the day Hillel didn't have enough money to get into the study hall of Shmayah and Avtalyon, so he climbed up on the roof and listened to them through the skylight, and he became buried in snow (Yoma 35b). Shmayah and Avtalyon certainly lived in Eretz Yisroel like all the Nesi'im, so how could Hillel have studied under them?
The answer is that he temporarily left Babylonia and came to study in Eretz Yisroel (taking his wife and children along with him, as we see from the story in Yoma 35b that he would give half his wages to his wife and the other half to the guard at the door of the Beis Medrash). It was common in Talmudic times for students to go and study in other countries, as the Gemara says in Eiruvin 54b, "What is the meaning of the verse, 'riders of white donkeys'? These are Torah scholars who go from city to city and from country to country to study Torah. Why are they called white? Because they make the Torah as clear as noon." Similarly, Tosafos in Kiddushin 29b says that scholars from Babylonia used to travel to Eretz Yisroel to memorize the Mishnaic teachings of the Tanaim, and sometimes the other way around: the scholars of Eretz Yisroel would travel to Babylonia to study Torah. And as the Mishnah in Avos 4:14 says, "Exile yourself to a place of Torah."
However, the Sifri seems to indicate that Hillel moved to Eretz Yisroel long before he was appointed Nasi. For on the verse, "And Moshe was 120 years old" (Devarim 34:7) the Sifri says, "Hillel the Elder came up from Babylonia when he was 40 years old, he studied under the Sages for 40 years, and then he led Israel for 40 years." But perhaps the Sifri does not mean that he moved permanently with his family to Eretz Yisroel at age 40, only that he traveled there periodically to study under the Sages of Eretz Yisroel. Although he was not in Eretz Yisroel all the time, even one day out the year is considered like an entire year, as we find in Chagigah 5b the story of Rav Idi who used to travel for three months just to spend one day in yeshiva, and in reference to him Rabbi Yochanan expounded the verse, "They seek me day by day" - this teaches that one who studies Torah for one day out of the year is considered as if he studied the entire year. Accordingly, it could be that Hillel's permanent residence was Babylonia, but once he reached 40 years of age he began to travel around to various countries to learn under different sages - because a given student cannot necessarily learn from just any teacher - until he was finally appointed Nasi and he moved permanently to Eretz Yisroel. The Sifri just says that he went up from Babylonia at age 40; it doesn't say where he went, so perhaps he went to several countries to seek Torah knowledge. The Gemara, in any case, implies that Hillel did not come to Eretz Yisroel until he was appointed Nasi, as I have written.
The Yerushalmi in the sixth perek of Pesachim tells the same story about Hillel and the Bnei Beseira, with some added details. The Bnei Beseira at first did not accept Hillel's teaching that the korban pesach could be slaughtered on Shabbos, and they said, "We have already said that there can be no hope from a Babylonian." The Pnei Moshe explains that in that generation, they did not rely much on the traditions of the Babylonian Jews. The Yerushalmi further states, "Hillel came up from Babylonia because of three questions." So we see that he had just then come from Babylonia, because of these three unanswered questions. One of the three questions is mentioned in the Toras Kohanim, Parshas Tazria, end of section 9: If a person has leprosy, and the kohein inspects him and erroneously declares that he does not have leprosy, is he then clean? The answer is no, and it is derived from the verse, "He is clean, and the kohein shall pronounce him clean." Only if he is truly clean can the kohein pronounce him clean. And the Toras Kohanim concludes: "Because of this question Hillel came up from Babylonia." The Raavad gives two explanations: either Hillel himself was uncertain about the meaning of the verse, so he went up to Eretz Yisroel to ask Shmayah and Avtalyon, or else the Jews of Eretz Yisroel were uncertain and they sent a letter to Babylonia asking Hillel to come up and teach it to them. The Korban Haeidah commentary on the Yerushalmi follows the first explanation of the Raavad, while the Pnei Moshe follows the second. We see from this that at most, it was only about these three questions that Hillel had some doubts and had to learn from the sages of Eretz Yisroel; all the rest of the Torah he knew, he learned in Babylonia.
At the beginning of that chapter of the Yerushalmi, the Pnei Moshe offers an interesting explanation of how Hillel could have learned most of the Torah he knew in Babylonia, yet studied under Shmayah and Avtalyon. He says that Shmayah and Avtalyon left their positions in Jerusalem and went to Babylonia, and there Hillel studied under them. [According to this, there would be no proof that there was a long chain of Torah scholarship in Babylonia, because perhaps Hillel learned all his Torah from Shmayah and Avtalyon, the scholars of Eretz Yisroel, during their stay in Babylonia.] The Pnei Moshe does not cite any source to back this up. The Yerushalmi does say, "They [Shmayah and Avtalyon] used to live near you." But that is not a conclusive proof that they left. In any case, it is clear that Hillel learned most of his Torah in Babylonia – whether Shmayah and Avtalyon were his teachers there or not.
We can bring proof from Rashi in Kiddushin 71 that Hillel did not come to Eretz Yisroel until the day he was appointed Nasi. There the Gemara says, “In the days of Rebbi there were some who wished to issue a ruling that the lineage of Babylonia Jews is inferior to that of Eretz Yisroel Jews. Rebbi said to them: You are putting thorns between my eyes.” Rashi explains that Rebbi was from a Babylonian family, from the descendents of Hillel, who came up and was appointed Nasi instead of the Bnei Beseira.
Another example of an important sage who lived outside of Eretz Yisroel during the Second Temple era was Rabbi Yehuda ben Beseira. The Gemara in Pesachim 3b tells the famous story of how Rabbi Yehuda ben Beseira met a non-Jew who boasted of having masqueraded as a Jew and eaten from the korban pesach offering. The sage advised him to ask for the tail next time, knowing that would raise suspicion since the tail is burnt on the altar and not eaten. Tosafos asks why Rabbi Yehuda ben Beseira himself did not come to Jerusalem for Pesach, and one of his answers is that he lived in Netzivin, outside of Eretz Yisroel, and Jews living outside of Eretz Yisroel are not obligated to come up to the Temple on festivals. [Netzivin today is located in southern Turkey and is known as Nusaybin.]
We see that Tosafos only grappled with the problem of why Rabbi Yehuda ben Beseira did not come to Jerusalem for festivals, but the fact that he lived outside of Eretz Yisroel did not bother Tosafos at all. In light of the Ramban, we understand why: the Divine remembrance at the time of Ezra was only for the Jews of Babylonia, not other countries. However, the Ramban does not explain why Hillel and other sages lived in Babylonia itself during the Second Temple period. For that we have to look to the Pnei Yehoshua, who says that not all the Jews of Babylonia were supposed to ascend, since the time of redemption had not yet arrived.
Perhaps even the Ramban could agree to the Pnei Yehoshua. When the Ramban says that there was no Divine remembrance for the other countries, he means that the Jews in the other countries were not permitted to come back to Eretz Yisroel at all, while the Jews of Babylonia were permitted to come back partially - but not all together like a wall. The reason was, as explained above, that due to the sin of idolatry during the First Temple period, a sin that was not sufficiently corrected, the time had not yet come for the the final redemption, and so it was only a temporary, partial remembrance.