The Baraita of the Forty-nine Rules (Hebrew: ברייתא מ"ט מדות) is a work of rabbinical literature which is no longer in existence except in references by later authorities. Rashi, the Tosafists, Abraham ibn Ezra, Yalḳut, and Asher ben Jehiel mention a work, "Baraita of the Forty-nine Rules," and make citations from it (thus, Rashi, ed. Berliner, on Ex. xxvi. 5; Yalḳ., Gen. 61, calls it "Midrash"; Rashi on Ex. xxvii. 6 calls it "Mishnah").
Samson ben Abraham (c. 1150–c. 1230), also known as the Rash of Sens (an acronym of his name) or "the Prince of Sens", was one of the leading French Tosafists in the second half of the 12th and the beginning of the 13th centuries.