The Beit Yosef is Karo’s magnum opus — by his own account the work he cared about most. Written as a commentary on the Arba’ah Turim of Rabbi Yaakov ben Asher, the standard code of his day, it does far more than explain. For each law it goes back to the Talmud, gathers the views of the great authorities who came after, and reaches a decision.
The method
To decide between the authorities, Karo relied on the three pillars of halachah: the Rif (Rabbi Yitzchak Alfasi), the Rambam (Maimonides) and the Rosh (Rabbeinu Asher). Where two of them agreed, he ruled with the majority. Where they were silent, he turned to the next great generation — the Ramban, the Rashba and the Ran. The rule was simple, transparent and could be checked by anyone with the sources in front of them.
Twenty years
Karo began the work in Adrianople around 1522 and completed it in Tzfat in 1542, then continued to revise it for more than a decade. It was printed, together with the Tur, in four great volumes: Orach Chaim and Yoreh De’ah in Venice (1550–1551), Even HaEzer and Choshen Mishpat in Sabbioneta (1553 and 1559). On the printed page the lines of the Tur sit at the centre, surrounded by the Beit Yosef.
Its influence
The Beit Yosef became the indispensable companion of the Tur and the great reference work of halachic sources. Its very success worried some sages, who feared that students would stop learning the sources themselves; one of them, Rabbi Yosef ibn Lev, changed his mind after a remarkable lapse of memory (see The Source That Would Not Come). Karo’s supplements and corrections were later published as Bedek HaBayit.
