French tosafist of the second half of the twelfth century. He was a pupil of R. Jacob b. Me�r (Tam), with whom he discussed legal questions. ?ayyim was the maternal grandfather of Moses of Coucy, author of the "Semag" ("Sefer Mi?wot Gadol"), and of Na?man ha-Kohen, author of "Na?moni," quoted in the responsa of Joseph Colon (No. 149). He is quoted in the Tosafot to Ber. 35a, Pes. 118a, ?id. 25b, and in other places. He is also mentioned in "Haggahot Mordekai," at the end of tractate Ketubot. Though a Kohen, he expressed his willingness to participate in the funeral of R. Tam, because "great men do not defile" (Ket. 103b).