The Rivash ריב״ש

Isaac ben Sheshet Perfet was born in Barcelona in 1326 and served as rabbi in Zaragoza, Calatayud and Valencia. In the summer of 1391 massacres swept Spain; he survived and some years later moved to North Africa — first to Miliana, then to Algiers, where he died in 1408.

About five hundred of his responsa survive. They are at once a body of rulings and a chronicle: the questions show what the communities were living through — how to divide the taxes, what to do with the property of those who had converted, whether the testimony of anusim may be accepted, what to do about a wife whose husband disappeared in a pogrom.

He was also among the first to speak cautiously and negatively about praying while directing oneself to the sefirot: prayer should be directed to God alone. That passage was much cited afterwards in arguments about Kabbalah.

In Algiers he faced a community living by its own customs while the arriving Spaniards lived by theirs; his responsa of that period are about how two customs are to share one town.