Moses Maimonides’ epistle to Yemen is now considered one of his most important works, one that shows the great philosopher and jurist playing a pastoral role as he addresses the needs and fears of a community in crisis. Shortly before the time of its writing, a charismatic Muslim leader had seized Yemen from the Fatimid caliphate; upon his death, his son and successor began persecuting Yemenite Jews. Dor Saar-Man explains how these circumstances led to Maimonides’ famous letter, and its legacy:
[I]n the year of 1172, a Yemenite Jew . . . presented himself as the messiah, . . . and many Jewish communities started to believe the messiah was actually coming soon and even started to change some of their practices and prayers accordingly. . . . Rabbi Yaakov ben Nathaniel of Yemen wrote to Maimonides with fear about the hard times the community was going through and wondered whether that new person might be the true messiah. Maimonides . . . replied at length, with empathy and attention.
In his detailed response, Maimonides tried to console Rabbi Yaakov and asked him to pray diligently and to keep in mind that troubles come and go and will eventually pass. He urged him not to surrender to persecutions and forced-conversion decrees, as these had happened in the past and yet the Jews prevailed. Maimonides referred to both Islam and Christianity as false religions and urged the Yemenite Jews not to conduct calculations of the end of times. . . . As for the messianic pretender, Maimonides clearly stated that he was a false messiah, a madman not to be trusted. . . .
The messianic enthusiasm in Yemen died out a few years later. . . . Saladin occupied Yemen and founded the Ayyubid dynasty, and everything returned to normal. The Yemen epistle, however, retained its significance and influence for centuries. . . . More than any other Jewish community, the Yemenites studied Maimonides’ work and accepted his theories. In time, two sub-groups were formed among them: the Shami, who partly assimilated into the Sephardi culture and adopted the Sephardi liturgy, and the Baladi, who followed Maimonides, especially the halakhic rulings set forth in his code, the Mishneh Torah.
Read more on Beit Hatfutsot: https://www.bh.org.il/blog-items/maimonides-jews-yemen-hand-hand-eight-centuries/