רב שמעון קיירא

Rav Shimon Kayyara, known for all generations as the Bahag — the Baal Halachot Gedolot — was a posek of the era of the Geonim, apparently of the city of Basra in Bavel, who lived around 4600/840. Almost nothing is known of his life beyond his great sefer. Though he lived in the days of the Geonim he never held the office of rosh yeshiva, and so he does not carry the title Gaon; some hold that he was close to the yeshiva of Sura and its derech, and that his sefer held a special standing among the Geonim of Sura. His name, it is explained, comes from a trade — a dealer in pitch or wax.

The Halachot Gedolot is one of the earliest codes of halachah: built upon the Halachot Pesukot, woven together with the She’iltot of Rav Achai and with further passages from the Talmudim and from the oral traditions that lived in the yeshivot of the Geonim; he was among the first of that era to draw on Torah of Eretz Yisrael from after the days of the Mishnah. Rav Avraham Ibn Daud in the Sefer HaKabbalah, and the Geonim Rav Sherira and Rav Hai, name Rav Shimon Kayyara as its author, while Rashi and the Baal HaSemag ascribed it to a Gaon named Rav Yehudai. The accepted view follows the first opinion, for the sefer cites Rav Tzemach bar Paltoi, who was niftar in 4650/890 — a century and more after the days of Rav Yehudai Gaon.