Abu ʿUbayda (d. 825) was a mawlā (client) of Jewish descent who wrote prolifically about history, religion, and culture. As such, he exemplifies the well-known feature of early Islamic learning that is the Abbasid-era mawlā scholar. His grandfather was a freeborn convert, rather than the more common manumitted slave, and it happens that the grandfather's patron—his sponsor, as it were, for admission into Islamic society—was a slave trader named ʿUbayd Allah b. Maʿmar (d. ca. 665). And ʿUbayd Allah b. Maʿmar, on a conservative estimate, had purchased hundreds of slaves from ʿUmar b. al-Khattab, the caliph who, before his assassination by a slave, had presided over the explosive early phases of the Islamic conquests.