Rambam רמב"ם
codifier of all halakhah, philosopher, physician to the sultan
Rambam was born in Córdoba in 4898. As a boy he fled the Almohads with his family: Spain, Morocco, a brief stay in the Land of Israel, and finally Egypt. In Fustat he became physician to Saladin's vizier and head of the Jewish community. He described his day as patients from morning to night, with Torah in what strength remained.
Under those conditions he did three things. A commentary on the Mishnah, whose introduction sets out the thirteen principles of faith. The Mishneh Torah, a code covering the whole of Jewish law, including the laws of Temple and kingdom, written in clear Hebrew without citations, «so that a person should need no other book». And the Guide for the Perplexed, for those who had studied philosophy and could not reconcile it with Torah — a book about what may and may not be said of God.
He was fiercely opposed: rabbis in Provence and northern France attacked the Guide and copies were burned. Yet the Mishneh Torah became the foundation of all later halakhah.