JOEL BEN ISAAC HA-LEVI (1115?–1200), one of the eminent talmudic scholars of Mainz. Little is known about his life. He was related on his maternal side to some of the most distinguished families of the generation, including that of *Samuel b. Natronai (his cousin, or uncle, later his brother-in-law) and *Eliezer b. Nathan (his father-in-law). He himself founded a family of talmudic scholars, beginning with his son *Eliezer, and leading to *Mordecai b. Hillel, five generations later. He acquired the foundation of his learning at Regensburg and is known to have spent some time in Wuerzburg, and also lived for a period in Cologne; but his place of residence was Bonn and he is referred to in literary sources as R. Joel of Bonn (Sefer ha-Terumah, 130 et al.). His teachers in Regensburg were *Isaac b. Mordecai, *Ephraim b. Isaac, and Moses b. Joel. With Ephraim b. Isaac he had a sharp exchange of views concerning the eating of abdominal fat, a custom which he permitted contrary to the opinion of Ephraim. Although as head of a yeshivah he had many pupils, only *Ephraim of Bonn is known, apart from his son Eliezer. Quotations from his works have survived in the Sefer ha-Ravyah of his son Eliezer and in the works of many contemporary scholars with whom he carried on a correspondence, particularly in the Raban of Eliezer b. Nathan, and a little in the Yihusei Tanna'im va-Amora'im of *Judah b. Kalonymus; from there it is known that Joel was the author of talmudic novellae and decisions of tosafot to many tractates, and of numerous responsa. Several of his liturgical hymns, reflecting the horrors of the Second Crusade, are also known. He was held in great esteem by all his contemporary German and French scholars, and Isaac b. Samuel, the most distinguished French scholar of his time, refers to him with great admiration (Ravyah, 933). Joel's gentle nature is evidenced in the above-mentioned exchange of letters between himself and R. Ephraim, and in his decision on the proselyte of Wuerzburg (Ravyah 2,253–6), whom Joel not only befriended but even permitted to conduct prayers, contrary to the opinion of other scholars.
Davidson, Oẓar, index S. V. Yo'el ha-Levi mi-Bonn (ben Yiẓḥak); V. Aptowitzer, Mavo le-Sefer Ravyah (1938), 37–48, 164–87; Urbach, Tosafot, 171–4, 179–81.