Rashbi's Successor -- the Rebbe, leader of our generation

Rashbi revealed the Torah’s inner dimension (its secrets), and thus the lesson from Lag B’Omer is that we should increase in the revelation and dissemination of the Torah’s inner dimension. More particularly, we must fulfill the mission given us by the previous Rebbe, leader of our generation, and Rashbi’s successor — the mission of disseminating Chassidus.

Although “Your wellsprings shall spread forth to the outside” — the idea of disseminating Chassidus — was said concerning the teachings of the Baal Shem Tov, it applies to the revelation of the inner dimension of Torah in general — the teachings of Rashbi. In Rashbi’s generation, this inner dimension of Torah was revealed in great measure. Afterwards, it was again concealed, until the Arizal’s time, when “it became permitted and a mitzvah to reveal this wisdom” — and most especially after the revelation of Chassidus in general, and Chassidus Chabad in particular, wherewith the esoteric dimension of Torah was presented in an intellectual framework, enabling it to be understood and assimilated by each person.

Sicha of the Lubavitcher Rebbe, 17 Iyar, 5744 (1984)