Third in the line of leaders of the Chabad movement was Rabbi Menachem Mendel Schneersohn, popularly known as the "Tzemach Tzedek," after the title of his voluminous responsa.

Rabbi Menachem Mendel was born on erev Rosh Hashanah 5549 (1789). His mother was Devorah Leah, daughter of the founder of Chabad Chassidism, Rabbi Shneur Zalman of Liadi (1745-1812). Rebbetzin Devorah Leah passed away three days after the Menachem Mendel's third birthday, and from that day the young orphan was reared and educated by his illustrious grandfather.

The young lad's prodigious abilities soon became evident. By the time he was twelve he had written many treatises on matters of Halachic importance and had begun recording the Talmudic and Chassidic teachings of his grandfather, supplementing them with his own comments and explanations.

Rabbi Menachem Mendel’s Response, published in Vilna 1872.
Rabbi Menachem Mendel’s Response, published in Vilna 1872.

While still in his teens, he was appointed by Rabbi Schneur Zalman to engage in the necessary research and reply to the numerous Halachic inquiries pouring in from scholars in Russia and Europe.

When Rabbi Menachem Mendel was only eighteen years old, the manuscript of his famous Chassidic discourse, "Roots of the Precept of Prayer" (Shoresh Mitzvat HaTefillah), which he had tried to conceal, was discovered by his grandfather. Rabbi Shneur Zalman was so delighted with his find that he thereafter allotted more time for their study together.

Rabbi Menachem Mendel was only twenty years old when he was appointed to take charge of most of Rabbi Shneur Zalman's communal activities.