The Talmud (Shabbos 89a) describes the inner conflict of Jews who sinned with the Golden Calf. In their eagerness to find a replacement for Moses, the leader of their generation, an optical illusion they saw in the clouds above, a man on his death bed, finally convinced them Moses had died and could now be replaced. They had but a few more hours to wait for the completion of a full 40-day-hiatus, but their impatience tripped them up.
The essence of their sin was that they relied on their visual perception rather than abide by the words of the leader of the generation, who told them "At the end of 40 days I will arrive, before noon" (Rashi Ex.32:1).
This episode of the past, says the Arizal, bears significantly upon the future (Sha'ar Hagilgulim, Preface). He explains, that the last generation of exile, that which immediately precedes the Era of Redemption [ours!], will be a recycling of the first generation, the generation of Moses that sinned by the Golden Calf. (The souls of the former generation will be recycled into the bodies of the latter generation.) Why? In order to amend the sin of the Golden Calf, those Jewish souls will have to withstand the same test a second time, but this time succeed. In that which they failed the previous time they must pass the next time. Which means those souls of the first generation will receive the very same trial, for only a triumph over the very same trial can rectify the sin that discredited them in the first place. Only a passing of this trial can uproot and eliminate the sin they bore since (Maimonides; Rules of Repentance, Chpt 2, Law 1).
And just like they dropped from so high a level, as when they tangibly experienced the divinity of God during the event of the Ten Commandments at Mount Sinai, to so low a level as worshipping an idol, so too rectification by this same trial will reverse their low state and allow them to regain the high ground, in fact to be launched to an even higher level of experiential holiness than ever before, namely, into that of the Era of the Final and Ultimate Redemption.
What then is that same trial? They will perceive the death of the leader of their generation and the test will be
to heed his words without letting their physical perceptions draw them to run afoul of his exhortations. The Rebbe told us we are the last generation of exile and the first generation of redemption (many scores of references, beginning with Bosi Legani, 1951). He expects us to believe this, despite what apparently seems as the disappearance of the leader of this generation, as if to signal the dawning of a new generation.
The same trial indeed manifests today. The Rebbe they say is dead and buried; That nature had taken its unwavering course and our perceptions, those of fleshy eyes, concur with this assessment. We saw the Rebbe shrivel with age, become ill and finally, after a hospital stay, interred at the Montefiore Cemetery.
Are we to believe the Rebbe's words now, when before he said, "Whereas for the leader of this generation -
interment is inapplicable, any more than it is applicable to the Rock of the Shtiya [in Jerusalem's Temple in the Holy of Holies]" (Shoftim, Elul 7, 5752), or who said, "There is a reality of Moses, the first redeemer is the last redeemer -
a soul in an eternal body." (Ha'Azinu, Shabbat Shuva 5750), (and many dozens more such pronouncements)?
And if the Rebbe said "A Rebbe's response is after all 'The words of God He spoke to me and His words are on my tongue' (quoting Shmuel the Prophet 2:23:2)", should we not listen to him, even if it conflicts with our senses?
Thankfully we have plenty of Torah sources to support us in this last period of our struggle. Rashi told us what to expect, "In the future, our Moshiach will conceal himself after he will have revealed himself, only to again reveal himself" (Daniel 12:12).
Said Rabbi Brachya, in the name of Rabbi Levi, "Just as what happened to the first redeemer will happen to the last redeemer - just as the first redeemer revealed himself to them and then goes and is concealed from them, so too the final redeemer reveals himself to them and goes on to conceal himself from them" (Midrash Rabba: Bamidbar 11:2, Ruth 5:6; Psikta Rabati 15; Psikta of Rav Kahana5:8).
"His sovereignty was temporarily placed in limbo, regarding the first redeemer, so too the last redeemer will be concealed, then return and be revealed." (Yalkut Shimoni Ruth 2:603).
"My beloved resembles a deer, just as a deer is spotted and then disappears, is spotted and then disappears, so too the first redeemer is seen, disappears, and then reappears ... Yehuda in the name of Rabi says to Kirsin, so too the last redeemer is revealed to them and, in turn, is concealed from them." (Midrash Rabba Shir Hashirim 2, 9:3)
Chassam Sofer (שמות ד'ה למה זה שלחתני): "And this was a great trial that he [Moses] disappeared for 6 months, and so will be in the days of Moshiach our Righteous, he will disappear after his revelation, as the Midrash tells us."
Sfas Emes (Rosh Hashana 11) writes, "It is rudimentary that the arrival of the son of David is separate from the redemption, for after all Moses arrived to Egypt before the redemption and could thus be revealed and be concealed, etc., similarly with the last redeemer, etc."
Rabbeinu Bechaye (Exodus 5:22): "And know that the issues of the first exile resemble issues we will face in the last exile ... and so the future redeemer will be revealed and, in turn, will be concealed, for this redemption will resemble the Egyptian redemption in many ways ... and once the threshold time nears, plenty of troubles will befall and wax - and this is the sign for Israel's salvation."
Midrash Pirkei Haychalot (Rabati 35:6): "At that time Jewry will change their minds; They will scoff Moshiach and say, 'Woe for us that we mistakened him for Moshiach'. God said to them, 'Now you will see his light ... and all who believed in him cannot be wiped from the book of life."
Ramban (ראה באור הרמב'ן על פרשת הנה ישכיל עבדי):
He says, initially Moshiach will reveal himself only to "that sect that yearns for him" [his chassidim, I suppose]. "And scripture relates concerning Moshiach, 'When many will put you to waste, etc.' that is to say when they lay you to waste - by mocking you in your first stage of arrival...."
The Holy Arizal (Sefer Gilgulim, preface, chpt 13) [NOT Sha'ar Hagilgulim]: "Moshiach will reveal himself and he will be recognized by few people, whereas others will not yet recognize him. Afterwards Moshiach will recede from view, as body and soul ... after which Moshiach will be revealed completely, then they will recognize him and all of Jewry will gather to him."
Joab 19:25: "And I knew my redeemer lives".
Midrash Raba, Shir Hashirim 2:25: "And he who believes him and follows him and awaits him - lives".
Psikta Rabati 35: "And your King Moshiach will come ... and God proclaims to the righteous of the generation and says to them 'Righteous of the world! Even though words of Torah endear you, it isn't nice of you that you waited for my Torah but did not wait for my kingdom."
See too
here what Rabbi Nachman of Breslov had to say about this precursor era.