EPSTEIN, ARYEH LEIB BEN MORDECAI (1705–1775), rabbi and kabbalist. Epstein was born in Grodno and was a pupil of Isaac of Grodno, Poland, and Aryeh Leib b. Nathan of Slutsk. After a brief period as a merchant he took up the position of preacher in Grodno and in 1741 became rabbi in Berestovitsa and Golynka. In 1745 he went to Koenigsberg, where he developed an extensive educational system. He sided with Jonathan *Eybeschuetz in the latter's dispute with Jacob *Emden, sharply criticizing the bickering in rabbinical circles. Two inquiries which he sent to Eybeschuetz in 1758 are extant, the one dealing with a halakhic matter, the other with the liturgy. Epstein was responsible for the introduction of a number of important takkanot in the Koenigsberg community and also for the establishment of the Great Synagogue there.
His works include Or ha-Shanim, on the 613 commandments (Frankfurt on the Oder, 1754); Sefer ha-Pardes, consisting of novellae to tractate Shabbat; sermons; funeral orations; a treatise on positive and negative commandments called Yalkut Sakhar va-Onesh, with an appendix entitled Kunteresha-Re'ayot on Shulḥan Arukḥ, Oraḥ Ḥayyim (Koenigsberg, 1764); and Mishnat Gur-Aryeh, a commentary on Isaac *Luria's prayer book (published in part only, Koenigsberg, 1765). He also published his responsa under the title Teshuvot Maharal (Morenu ha-Rav R. Aryeh Leib; ibid., 1769); wrote glosses to the Talmud (together with his son Abraham Meir); glosses and novellae to Shulḥan Arukh, Yoreh De'ah, to which his son also contributed (Vilna, 1883); and several other works.
J. Emden, Mitpaḥat Sefarim (Lemberg, 1870), 119; D. Kahana, Toledot ha-Shabbeta'im ve-ha-Ḥasidim, 2 (1914), 57; S.A. Friedenstein, Ir Gibborim (1880), 41, 44ff., 47–50; E.M. Epstein, Gevurot ha-Ari (18882); H.N. Maggid (Steinschneider), Ir Vilna (1900), 44; Sefer Yahadut Lita, 3 (1967), 30.