the Maggid of Mezritch המגיד ממזריטש
successor of the Baal Shem Tov, who turned Hasidism into a network of courts
Rabbi Dov Ber was a formidable Talmudist and kabbalist, weakened by fasting and ill when he first came to the Baal Shem Tov — more out of doubt than faith. Tradition says the Besht asked him about a difficult passage in the writings of the Ari, explained it, and the room filled with light. He stayed, and became the foremost disciple.
After the Besht's death in 5520 he moved the centre to Mezritch and did what his teacher had not: he built a system. Gifted young men came to him; he taught them and sent them out to found communities. From his school came Rabbi Elimelech of Lizhensk, Rabbi Levi Yitzchak of Berdichev, Rabbi Shneur Zalman of Liadi, Rabbi Aharon of Karlin and Rabbi Menachem Mendel of Vitebsk, who went up to the Land of Israel. In one generation Hasidism turned from a circle into a movement.
His own teaching is the most profound of early Hasidism: on «ayin», on the self-effacement of a person before the infinite light, on thought preceding speech.