Rashbi, Moshe, the Alter Rebbe: Souls of Atzilus

There are souls that even while they are in this world they are souls of [the highest spiritual world of] Atzilus. Like the souls of Rashbi and the souls of Moshe Rabbeinu and also the soul of the Alter Rebbe [Schneur Zalman of Liadi, the Baal HaTanya]. From this it is understood that it also applies to those who filled his [the Alter Rebbe's] place, each Nosi* in his generation, as they are souls of Atzilus. Because the Nosi of every generation is an extension of Moshe** and he was a soul of Atzilus. And all the moreso the Rebbes of Chassidus, whose labor is the spreading of the wellsprings outward, to disseminate the wellsprings of Rashbi, who was also a soul of Atzilus as was mentioned.

The Lubavitcher Rebbe, from the Chassidic discourse "Lehovin Inyan Rashbi" 5730 (1980)

* Nosi [Nasi]: spiritual head of the Jewish people

** Tikkunei Zohar, Tikkun 69