Dov Ber ben Avraham of Mezeritch (Yiddish: דֹב בּער פֿון מעזעריטש; died December 4, 1772 O.S.), also known as the Maggid of Mezeritch or Mezeritcher Maggid, was a disciple of Rabbi Israel ben Eliezer (the Baal Shem Tov), the founder of Hasidic Judaism, and was chosen as his successor to lead the early movement. Dov Ber is regarded as the first systematic exponent of the mystical philosophy underlying the teachings of the Baal Shem Tov, and through his teaching and leadership, the main architect of the movement. He established his base in Mezhirichi (in Volhynia), which moved the centre of Hasidism from Medzhybizh (in Podolia), where he focused his attention on raising a close circle of disciples to spread the movement. After his death the third generation of leadership took their different interpretations and disseminated across appointed regions of Eastern Europe, rapidly spreading Hasidism beyond Ukraine, to Poland, Galicia and Russia. His teachings appear in Magid Devarav L'Yaakov, Or Torah, Likutim Yekarim, Or Ha'emet, Kitvei Kodesh, Shemuah Tovah, and in the works authored by his disciples. His inner circle of disciples, known as the Chevraia Kadisha ("Holy Brotherhood"), included Rabbis Avraham HaMalach (his son), Nachum of Czernobyl, Elimelech of Lizhensk, Zusha of Hanipol, Levi Yitzchok of Berditchev, Boruch of Medzhybizh, Aharon (HaGadol) of Karlin, Chaim Chaykl of Amdur, Menachem Mendel of Vitebsk, Shmuel Shmelke of Nikolsburg, Shlomo Flam (the Lutzker Maggid), Asher Zebi of Ostrowo, Zev Wolf of Zhitomyr, and Shneur Zalman of Liadi. Source: Wikipedia (en)