Although by no means the most important Jewish community of the medieval Muslim world either numerically or culturally, Egyptian Jewry is certainly the best–known to modern historical scholarship, or at least the most intimately known with regard to its quotidian life during the Islamic High Middle Ages, owing to the rich documentation that has survived in the Cairo Geniza. The Geniza was a vast repository of discarded written materials – sacred and secular, literary and documentary – that was attached to the Ben Ezra synagogue in Fustāt (Old Cairo). Emptied of its contents in 1896, the Geniza was found to contain over a quarter of a million manuscripts and fragments dating back as far as the mid-eighth century, although the lion’s share of the material dated from the tenth to the thirteenth centuries, that is from the Fātimid, Ayyūbid, and early Mamlūk periods.

Egypt had always been the foremost center of Hellenistic Jewry. However, by the time of the Arab conquest, the heyday of the Egyptian Jews had long passed and their numbers were considerably reduced in the suppression of Jewish uprisings during the first two centuries of the Common Era and later, as a result of Byzantine Christian persecution. Still, the number of Jews was large enough to impress the Muslim conquerors from the Arabian desert. According to the early chronicler Ibn ‘Abd al–Hakam, there were 40,000 Jews in Alexandria alone when the city fell to the Muslims in 642. Although the actual figure was probably closer to 4,000, it is a good indication of the rude desert Arabs’ sense of wonder and amazement at the size and sophistication of the large urban Egyptian Jewish community.