Database: Arabic as a Cultural Unifier
Long a linguistic presence in the Arabian Peninsula and the Eastern Mediterranean, Arabic expanded all over the empire through the conquests of the seventh and eighth centuries and the establishment of Arabic-speaking diasporas and colonies. Through a combination of deliberate policies and peer pressure, it eventually became the lingua franca of much of the territory stretching from the Pyrenees to the Himalayas.
Many factors explain the expansion and popularity of Arabic. First and foremost, it was the liturgical language of Islam and its mastery was necessary to read and understand the Quran and other religious texts. The slow and steady spread of this religion across the empire therefore led to the adoption of its sacred language by the new converts. Moreover, by the 720s, much of the administration of the empire had become Arabicized. Those wishing to advance socially and politically therefore found it well worth their effort to learn Arabic. Finally, as something akin to a common tongue, it became the language of trade, arts, and sciences between the various peoples of the empire.
Despite being the dominant language of the empire, Arabic was not the only language spoken in it. Among other languages spoken were Persian in Iran, Syriac in Syria, Berber in North Africa, Coptic in Egypt, and Hebrew wherever there was a Jewish community. It is probable that most inhabitants of a cosmopolitan city like Baghdad spoke a little bit of multiple languages. de:Das Arabische als kulturelle Bindeglied