Baal Halakhot Gedolot (Bahag)

Shimon Kayyara was a Babylonian halachist of the early Geonic period — most scholars place him in the first half of the ninth century (some traditions, the eighth) — known by the title Bahag, 'the author of the Halakhot Gedolot.' His Halakhot Gedolot was among the very first comprehensive codes of Jewish law after the Talmud, organizing the vast Talmudic material by subject and including a celebrated enumeration of the 613 commandments that later authorities debated for centuries. Though he lived in the academies of Babylonia, he was never formally appointed a Gaon. (Authorship has occasionally been ascribed instead to Yehudai Gaon, but tradition and most scholarship credit Kayyara.)