Sifre (Hebrew: סִפְרֵי; siphrēy, Sifre, Sifrei, also, Sifre debe Rab or Sifre Rabbah) refers to either of two works of Midrash halakhah, or classical Jewish legal Biblical exegesis, based on the biblical books of Bamidbar (Numbers) and Devarim (Deuteronomy).
The title Sifre debe Rab (lit. "the books of the school of Rab") is used by R. Hananeel on Sheb. 37a (while citing Sifrei on Numbers 6:9), Alfasi on Pes. x., and Rashi on Hos. ii. 1, while citing a passage taken from Sifrei on Numbers 25:1; it occurs likewise in Mak. 9b, where, as Berliner says in his edition of Rashi, p. 372, בספרא is an error for בספרי; comp. Arukh, s.v. ארבע, where he cites Sifrei on Deuteronomy 6:4). The 8th century author of Halakhot Gedolot names four "exegetical books belonging to the Scribes" (Heb. Midrash sofrim) and which, in all appearances, seem to refer to "Sifre debe Rab" and which comprised the following compositions: 1) Breishit Rabba (i.e. the first book of the Midrash Rabba), 2) Mekhilta (on the Book of Exodus), 3) Sifrei (on the Book of Numbers) and 4) Sifrei (on the Book of Deuteronomy). In regard to the reference in Sanh. 86a concerning the Sifre of R. Simeon, see Mekilta de-Rabbi Shim'on; the question has likewise been raised whether, in view of the well-known close relation that existed between the school of R. Simeon and that of R. Ishmael (Yoma 59a; Zeb. 53b, 119b; Ḥul. 69b), the words וכלהו אליבא דר"ע apply to R. Simeon's Sifre in the same degree as to the other works mentioned in this Talmudic passage (Levy, Ueber Einige Fragmente aus der Mischnah des Abba Saul, p. 11, note 15).