Shabbos Parshas Va’Eschanon is also “Shabbos Nachamu”, the first of the “seven [Sabbaths] of comforting”, named after the haftorah which begins with the words “Nachamu Nachamu ami” (Be comforted, be comforted, My people).
The double expression of “Nachamu” (double-comforting following the destruction of the Beis Hamikdosh (twice) on Tisha B’Av) implies a true, unlimited comforting after the destruction of Tisha B’Av. (The Rebbe points out that: “Since the comforting is (not only words of comfort and the like, but rather) through the rebuilding of the Beis Hamikdash.” — (one of the jobs of Moshiach.))
The first Beis Hamikdosh was primarily due to revelations from Above to below; the second was primarily an effort from below to Above. The third Beis Hamikdosh, which is eternal, (because it) will be a union of those two qualities. In other words (explained in footnote 52 in the original), the revelation of G-dliness that occurred in the first Beis Hamikdosh was so powerful that it nullified the worldly reality of those in this world; the second Beis Hamikdosh emphasized the integration of G-dly revelation into the worldly reality of those in this world. These will be unified in the third.
This primary difference between these two directions is that the integration of G-dly revelation into the worldly reality of those in this world (in a way which does not “shatter” their reality) takes a long time. Similar to the process of conquering and dividing Eretz Yisroel under Yehoshua, which took 14 years.
This is similar to the process of going from Tisha B’Av to the 15th of Av, of which our sages say “there were never Yomim Tovim for Yisroel like the 15th of Av….” What happened to cause the 15th of Av to receive such a description? The first, and main, event to happen on the 15th of Av is that those who were decreed to die in the desert ceased dying on that day. To explain:
Those who accepted the testimony of the meraglim about the land of Israel and didn’t want to enter were condemned to die in the desert on that same day, Tisha B’Av, during the next 38 years. Each year, on Tisha B’Av, those who reached 60 years old would dig graves, lie down, and would not wake up in the morning. In the final year, the last group followed the same procedure only they were surprised to wake up the next morning! They surmised that they had made a mistake in calculating the day of the month, so the next night they again lay down to die in their graves. But the next morning they also awoke! Thinking that they had erred in calculating the date, they did this again the next night, continuing until the night of the 15th when the full moon indicated that they had not erred in the date but, rather, the decree had been annulled by Hashem!
In other words: the decree had been annulled on Tisha B’Av itself, but it took until the 15th of Av for them to realize this, to internalize it and integrate it. Similarly, the “birth of Moshiach” on Tisha B’Av is not recognized immediately, but takes a long time to be realized, internalized, and integrated. The Rebbe expresses it that “when the moon is full it is known with certainty that Moshiach was already born on Tisha B’Av (similar to what we find regarding the establishment of the 15th of Av as a Yom Tov, even though the decree had been nullified on Tisha B’Av)”. The moon hints at the Jewish people, and the full moon means to receive the light of the sun [Moshe Rabbeinu is likened to the sun] in a complete and perfect manner.
Saying that Moshiach is “born” on Tisha B’Av means a dimension of his revelation (not his physical birth, see the Maharal* and Abarbanel). But even after Moshiach himself becomes spiritually “large”, the exile is drawn out in so that it will be in a complete and perfect manner also as regards its integration by those in this world.
So we understand from the Rebbe’s words that as far as the revelations from Above are concerned, Moshiach is here and nothing is lacking. But nonetheless the state of golus continues because the process of our accepting and integrating this new reality is a time-consuming process (which, of course, is up to us!).
Thus, the instruction of the Rebbe here is to emphasize again the need to learn matters of Geulah, especially in Pnimiyus Hatorah, in a way of “laboring” in Torah, “and may it be Hashem’s will that through contemplating these matters we should merit immediately to see the true and complete Geulah–Immediately, mamash”!
* Footnote 93 refers to Netzach Yisroel by the Maharal of Prague, page 132 which speaks of the birth of Moshiach. Towards the end of that page, the Maharal writes how Moshiach’s name is “Menachem”, the comforter, because just as the “comforter” must be distant and removed from the mourning of the one he is comforting, similarly Moshiach (Menachem) is distant and removed from the rest of the people due to his lofty and elevated spiritual level.