He writes in a sicha that the baal hatanya was greater than R Yochanan Ben Zakai because RYBZ was not in touch with his neshama , he was too busy with his avodat hashem so he had never time to check his neshama it should not be in the kelipa .
This “quote” from the “Rebbe” may seem shocking to some of the readers (it was quoted often in the anti-Chabad rhetoric of the 80s), so allow me to clarify the source:
Rav Yochanan Ben Zakai cried on his deathbed that he doesn’t know which path they will take him. (Brochos 28b)
The Baal Hatanya explained that he was on an extremely high level of intellect which concealed his emotions, which led to his question.
The Rebbe Rashab said (Toras Sholom – Yud Tes Kislev 5673) that he heard from the TZEMACH TZEDEK (no, not from the seventh rebbe) that the Baal Hatanya was on a higher level than RYBZ who didn’t know which path he would be taken, while the Baal Hatanya did (see the full story there).
On the other hand, the REBBE explains (Likkutei Sichos vol. 16 pg. 273) that every Yid must learn from the avoda of RYBZ! The main focus of ones life shouldn’t be on himself and which level one is holding, instead it should be on the job that he was given to accomplish in the world. Only on his deathbed did RYBZ have a chance to begin contemplating his spiritual status.
The Rebbe once spoke about this in a maamar (Shvat 5712) and he sobbed very much how every person is given a certain amount of days from Hashem, and we must learn from RYBZ to use out every single moment for avodas Hashem without wasting any time even for worrying about oneself.
Just to set the record straight so no one should be confused about what the Rebbe said or where he got it from.