"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 the Baal Shem Tov's "spiritual grandson," Rabbi Schneur Zalman of Liadi, the founder of the Chabad branch of Chassidism (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." He was soon accepted into the intimate circle of Rabbi DovBer's leading disciples. Though the youngest of the group, his greatness was recognized by his master and his colleagues, and he played a leading role in the leadership of the Chassidic community. After Rabbi DovBer's passing in 1772, a number of his disciples made aliyah to the Holy Land and established Chassidic communities there, while others fanned out throughout Eastern Europe to establish Chassidic "courts" in their respective provinces. Rabbi Schneur Zalman settled in his native province of "Riessin" (Lithuania and White Russia) where he 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.

For more on the Baal Shem Tov, Rabbi Schneur Zalman and Chassidism, see the 41 essays and stories, published over the last five years on Chabad.org and assembled below:

On Rabbi Israel Baal Shem Tov:

Revolution

The Baal Shem Tov's 16th Birthday

The High Road

The Baal Shem Tov's "Echad"

The Old Man on the Island

The Wandering Storyteller

Hidden and Revealed

Pushcart Prophet

The Master Key

The Ladder

The Prayerbook

The Baal Shem Tov's Mysterious Journey to Leipzig

The Baal Shem Tov on Love

The Truth About the Baal Shem Tov

Thirty-Six Aphorisms of Rabbi Israel Baal Shem Tov

On Rabbi Schneur Zalman of Liadi:

The Fork in the Road

The Splattered Gem

The Longer Shorter Way

Bonaparte and the Chassid

Faith and Reason

Body: The Physical World According to Rabbi Schneur Zalman of Liadi

Jacob's Stuff

Is Judaism a Theocracy?

Alienation and Faith

The Master of Song

The Ascent of the Tzaddik

Twenty Eight Teachings from Rabbi Schneur Zalman of Liadi

On Chassidim and Chassidism:

A Story of Three Sisters

The Lamplighter

A Man I Met in Shul

The Dancing Jews

Knowledge

One on One

Playing at "Rebbe & Chassid"

Spiritual Warrior

Chassidic Feminist

Seeking Farbrengen

The Abnormality of Jewish Life

Barrels in the Snow

On Elul 18

Man Alive: A Chai Elul Story

What Happened on Your Birthday?