Judah ben Isaac Messer Leon (1166–1224) was a Frenchtosafist born inParis.

Born in 1166 in Paris, France, his father Rabbi Isaac Treves was a rabbi in Paris, son ofYom Tov of Falaise who was the son ofJudah ben Nathan (Rivan), and thus a descendant ofRashi. In his early years, he learnt underIsaac ben Samuel ofDampierre and his sonElhanan ben Isaac of Dampierre. He married a daughter ofAbraham ben Joseph of Orleans, who has been identified by Jacobs^[1] with Abraham fil Rabbi Joce, chief Jew inLondon in 1186. In a list of that year associated with Abraham occurs the name of Leo Blund, whom Jacobs identifies with Judah ben Isaac.^[2]

Sir Leon must have leftParis in 1182, when all Jews were expelled from the French king's dominions; he did not return until 1198. According to Gross, however, he received his chief training atDampierre underSamson of Sens,Samson of Coucy,Solomon of Dreux, andAbraham ben Nathan ofLunel. Shortly after 1198 he returned to Paris and founded an important school of tosafists, in which were trained, among others,Jehiel ben Joseph (Sir Leon's successor),Isaac ben Moses of Vienna (author ofOr Zarua),Samuel ben Solomon of Falaise (Sir Morel of Falaise), andMoses of Coucy.

He appears to have composedtosafot to most of the tractates of theTalmud, traces being found of his annotations to twenty tractates. The only collection that has been published are his additamenta toBerakot, published atWarsaw in 1863. A long fragment of histosafot toAbodah Zarah is still extant in a manuscript that formerly belonged toSamuel David Luzzatto andSolomon Joachim Halberstam 'R.E.J.'s session ofJews' College,London. A few of hisresponsa are also found, chiefly in various additions to theMordecai, while reference is also found to his commentary on thePentateuch, in which he appears to have followed the method ofRashbam.

Judah wrote several poems—anAramaic description of theTen Commandments,^[3] apizmon,^[4] and apiyyut.^[5] He is not, however, to be identified with the mysticalYehudah HaChasid, to whom are attributedSefer Hasidim and anethical will. The writers whom Judah quotes includeAmram Gaon,Sherira Gaon,Hai Gaon,Nissim Gaon,Alfasi,Maimonides,Elijah ben Menahem,Gershom ben Judah,Jacob of Orleans,Jacob of Corbeil,Joseph Kara,Joseph Bekor Shor,Yom-Tov of Joigny, andRashi.

He died in Paris in 1224.^[6]

• Tosafists

 This article incorporates text from a publication now in thepublic domain: Solomon Schechter andJoseph Jacobs (1901–1906)."Judah ben Isaac". InSinger, Isidore; et al. (eds.).The Jewish Encyclopedia. New York: Funk & Wagnalls. Its bibliography:

• Henri Gross, in Berliner'sMagazin, iv.173-210;
• idem,Gallia Judaica, pp. 519–524;
• Joseph Jacobs,Jews of Angevin England, pp. 406–416.

• Rabbis from Paris
• 1166 births
• 1224 deaths
• 12th-century French rabbis
• French Tosafists
• 13th-century French rabbis

• Wikipedia articles incorporating a citation from the 1906 Jewish Encyclopedia
• Wikipedia articles incorporating a citation from the 1906 Jewish Encyclopedia without a Wikisource reference
• Wikipedia articles incorporating text from the 1906 Jewish Encyclopedia