Isaac ben Mordecai

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ISAAC BEN MORDECAI (known as Ribam, initials of R abbi I saac B en M ordecai; 12th century), German tosafist. Isaac was also known as Isaac b. Mordecai of Bohemia and Isaac b. Mordecai of Prague. The abbreviated form of his name, Ribam, led to his being confused at times with *Isaac b. Meir (see Urbach, Tosafot, 170 no. 37). Active in the community of Regensburg, he served as head of its bet din and was regarded as the greatest scholar of the town and its leader (as described by Jacob b. Meir *Tam in Sefer ha-Yashar, part of responsa ed. by F. Rosenthal (1898), 178 no. 80). He was a pupil of *Isaac b. Asher ha-Levi (Riba i) of Speyer and of Jacob Tam. He compiled tosafot to most tractates of the Talmud, a large part of them while with his teachers. A considerable part of his tosafot to Bava Batra are included in the printed edition of the Talmud and in the tosafot of *Isaiah di Trani. He is known to have written tosafot to the tractates Pesaḥim, Mo'ed Katan, and Bava Kamma compiled before his teacher, Isaac, and to Shabbat, Ketubbot, Gittin, Sotah, Nazir, and Bava Meẓia. He is quoted in the printed tosafot to Yoma, Ḥagigah, Sanhedrin, Zevaḥim, and Ḥullin, and in Sefer ha-Ravyah and Or Zaru'a. *Eliezer b. Nathan of Mainz sent his book to him and his colleagues *Ephraim b. Isaac and Moses b. Joel on the bet din of Regensburg. They criticized many of his statements and in his reply Eliezer treated them with great respect. He also sent them the well-known responsum on ḥallonot ("windows," i.e., the prohibition against disturbing the privacy of a neighbor by opening a window facing his premises).


Eliezer b. Nathan, Sefer Rabban, ed. by S. Albeck (1904), introd. p. xi; V. Aptowitzer, Mavo le-Sefer Ravyah (1938), 29, 42f., 288, 378f.; Epstein, in: Tarbiz, 12 (1940/41), 200–2; Urbach, Tosafot, 167–70.

[Shlomoh Zalman Havlin]

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Isaac ben Mordecai

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