"Chai Elul" -- the 18th day of the Hebrew month of Elul -- is a most
significant date on the Chassidic calendar. The founder of Chassidism, Rabbi Israel Baal Shem Tov, was born on this date, in 1698. It is also the day, 36 years later, on which the Baal Shem Tov began to publicly disseminate his teachings, after many years as a member of the society of "hidden tzaddikim" during which he lived disguised as a simple innkeeper and clay-digger, his greatness known only to a very small circle of fellow mystics and disciples.
Elul 18 is also the birthday -- in 1745 -- of Rabbi Schneur Zalman of Liadi, who often referred to himself as the Baal Shem Tov's "spiritual grandson" (Rabbi Schneur Zalman was the disciple of Rabbi Israel's disciple, Rabbi DovBer of Mezeritch). After gaining fame as a child prodigy and young Talmudic genius, Rabbi Schneur Zalman journeyed to Mezeritch to study under the tutelage of the Baal Shem Tov's successor--as he later explained, "to study I knew somewhat, but I needed to learn how to pray"--and was soon accepted into the intimate circle of Rabbi DovBer's leading disciples. Rabbi Schneur Zalman established the "Chabad" branch of Chassidism, which emphasizes in-depth study and intense contemplation as the key to vitalizing the entire person, from sublime mind to practical deed.