[In the past siman, the Rebbe brought proof from the words of Chazal that the oath against going up as a wall is not simply a prohibition on fighting the nations – and thus with their permission mass immigration would be allowed. Rather, the oath comes to enforce a Divine decree that we should be in exile until moshiach comes. In this siman, he quotes sources that give a Kabbalistic reason for that decree - to gather the holy sparks from around the world. He also brings the Midrash that says that not only is gentile permission not enough - even when moshiach actually does come, the Jews will be afraid to follow him, for fear that the decree of exile has not yet been fulfilled.]
The Midrash Rabbah on Shir Hashirim 2:8 goes even further.
The voice of my beloved, behold it has come.” This refers to the king moshiach. When he says to Israel, “In this month you will be redeemed,” they will say to him, “How can we be redeemed? Didn’t the Holy One, blessed is He, already swear that He would make us serve all seventy nations? And moshiach will give them two answers: “When one of you goes to exile in Barbary and another of you goes into exile in Sumatra (in the Pesikta Rabasi the text reads: Britain), it will be considered as if you all went to these places.” The second answer is: “The government appoints local governors from various nations around the world. If one Cuthean, for instance, becomes a ruler over the Jews, although the central government may not be Cuthean, it is considered as if the Jewish people were in exile under the Cuthean people. So it is as if you served all seventy nations.” Therefore, this month you will be redeemed.
We see here that even after moshiach comes, the Jews who believe in Hashem’s oath to send us into exile under all seventy nations will still be afraid, and they will say that it is impossible that there could be a redemption for our benefit before the oath of exile has been fulfilled. And although Chazal in the Midrash there have already revealed to us the answer to this question, it won’t be enough for the Jews at that time, until Hashem [speaking through His prophet, moshiach] will tell us so Himself, that the true end-time for redemption has really arrived. We will not be able to determine on our own whether the decree of exile has been fulfilled in the way described in the Midrash [possibly because we don’t know the exact identity of the Seventy Nations, or because we don’t know where every Jew has gone to exile, or because we don’t know what nation every governor descends from]. Only Hashem, who is all-knowing, who witnesses everything, and who surveys everything with a single glance, is capable of knowing this.
We see from all of these sources that for the entire Jewish people to come to Eretz Yisroel before the coming of moshiach violates Hashem’s oath and delays the redemption. [It delays the redemption because if Jews still have to fulfill the decree and go to live under certain nations, under which they have not yet lived, it will take longer to fulfill it, because they will have to leave Eretz Yisroel and go to those nations.]
And so it is written in the writings of the Arizal, Shaar Hamitzvos, Parshas Re’eh, under the mitzvah to remember the Exodus from Egypt, on the verse, “So that you should remember the day you left Egypt all the days of your life.” It is a long piece, but briefly, his point is that there is a difference between the redemption from Egypt and the other redemptions in our history, from Babylonia and Media and so on. In the redemption from Egypt, all the good souls were selected from Egypt and joined to the Jewish people, as the Torah says, “And they emptied out Egypt.” Therefore, there was no need for Jews to be there anymore. But in the other redemptions, the Jewish people were not completely redeemed – there still remained some souls there that needed to be selected. Therefore some Jews stayed on under the hand of Babylonia and Media, and did not ascend to Eretz Yisroel when the Second Temple was built, as is well known – in order to purify the souls remaining there.
The Arizal also writes that when the Midrash says that if one Jew goes to exile in a country it is considered if the whole Jewish people were exiled there, that is only talking about the rest of the Seventy Nations besides Babylonia, Media, Greece and Edom. But these four major exiles are the roots of all exile and a large part of the Jewish people needed to take part in them. The rest of the Seventy are merely branches of these four. The only Jews who must go to them are those whose souls’ sparks fell among that nation. Therefore they must go there to extract their fallen sparks.
We see from this two things:
1) When the Midrash says that one Jew going to exile in a country is enough, it is talking about those Jews going to places where the fallen sparks of their souls are to be found. This is something a person cannot know on his own; only Hashem knows. He manipulates events and guides a man’s footsteps, without the person’s knowledge, such that usually a person does not know why he has come to live wherever he lives.
2) Even when Ezra ascended, it was necessary that part of the Jewish people stay in Babylonia in order to rectify the souls that remained there, and certainly Ezra the Scribe agreed to this. I have explained this earlier (Siman 13) even on a simple (non-Kabbalistic) level.
Now, you may ask: the exile due to our sins, as we say, “Because of our sins we were exiled from our land.” If so, if there had been no sin, there would have been no exile. If there had been no exile, what would have become of all those souls and sparks?
The Ohr Hachaim Hakadosh on Parshas Behar (Vayikra 25:39) answers that question. He says there that one of the reasons why Hashem decreed exile on the Jews and did not just punish them in their land is in order to sort out the sparks of holiness from around the world. And then he continues, “And if you say, if this is so, then if the Jews had not sinned and gone into exile, who would have sorted out those sparks that are being sorted out now? You must know that had the Jews not sinned, they would have had the power to stay in Eretz Yisroel and extract the sparks of holiness from wherever they went in the world. But after their sins, they are weak, and we only hope they have enough power to do this job while living around the world in the places where the sparks are located.”