Arabic. Since God's original revelations to Muhammad between circa 610 and 632 first took the form of oral recitation and were later collected in the Qur'an, the Arabic language may rightly be considered intrinsic to the Islamic faith. The function of Arabic as a vehicle for communication within the Muslim community varied greatly over time and space. Initially, most if not all Muslims spoke Arabic and understood the Qur'an when they heard it recited. Though dialectical differences distinguished the Arabic of some parts of the Arabian peninsula from that of other parts, a pre-Islamic tradition of poetry used to extol the virtues or achievements of a tribe had produced a substantial degree of mutual comprehension of poetic diction, which is quite similar to the diction of the Qur'an.

Expansion. From 634 onward, when the first khalifahs rallied the far-flung Arab tribes to carry the Islamic conquests...