Isaac Alfasi
Isaac ben Jacob Alfasi ha-Cohen (1013 - 1103) (Hebrew: ר' יצחק אלפסי) - also known as the Alfasi or by his Hebrew acronym Rif (Rabbi Isaac al-Fasi), was a Talmudist and posek (decider in matters of halakha - Jewish law). He is best known for his work of halakha, the legal code Sefer Ha-halachot, considered the first fundamental work in halakhic literature. He was born in the Algerian city Al Qal'a of Beni Hammad, but spent the majority of his career in Fes, and is therefore known as "Alfasi" ("of Fes" in Arabic).