As the revelations granted to Muhammad became known in Mecca, they attracted a small following of some close relatives, a few prominent Meccan leaders, and an assortment of lower-class dependents, freed slaves, and members of poorer clans. Those teachings also soon attracted the vociferous opposition of Mecca’s elite families, particularly those of Muhammad’s own tribe, the Quraysh. Muhammad’s claim to be a “messenger of Allah,” his unyielding monotheism, his call for social reform, his condemnation of Mecca’s business practices, and his apparent disloyalty to his own tribe enraged the wealthy and ruling families of Mecca. So great had this opposition become that in 622 Muhammad and his small band of followers emigrated to the more welcoming town of Yathrib, soon to be called Medina, the city of the Prophet. This agricultural settlement of mixed Arab and Jewish population had invited Muhammad to serve as an arbitrator of their intractable conflicts. The emigration to Yathrib, known in Arabic as the hijra (HIHJ-ruh) (the journey), was a momentous turning point in the early history of Islam and thereafter marked the beginning of a new Islamic calendar.

The new community, or umma, that took shape in Medina was a kind of “supertribe,” but very different from the traditional tribes of Arab society. Membership was a matter of belief rather than birth, allowing the community to expand rapidly. Furthermore, all authority, both political and religious, was concentrated in the hands of Muhammad, who proceeded to introduce radical changes. Usury was outlawed, tax-free marketplaces were established, and a mandatory payment to support the poor was imposed.

In Medina, Muhammad not only began to create a new society but also declared his movement’s independence from its earlier affiliation with Judaism. In the early years, he had anticipated a warm response from Jews and Christians, based on a common monotheism and prophetic tradition, and had directed his followers to pray facing Jerusalem. But when some Jewish groups allied with his enemies, Muhammad acted harshly to suppress them, exiling some and enslaving or killing others. This was not, however, a general suppression of Jews since others among them remained loyal to Muhammad’s new state. But the Prophet now redirected his followers’ prayer toward Mecca, essentially declaring Islam an Arab religion, though one with a universal message.

From its base in Medina, the Islamic community rapidly extended its reach throughout Arabia. Early military successes against Muhammad’s Meccan opponents convinced other Arab tribes that the Muslims and their God were on the rise, and they sought to negotiate alliances with the new power. Growing numbers converted. The religious appeal of the new faith, its promise of material gain, the end of incessant warfare among feuding tribes, periodic military actions skillfully led by Muhammad, and the Prophet’s willingness to enter into marriage alliances with leading tribes—all of this contributed to the consolidation of Islamic control throughout Arabia. In 630, Muhammad triumphantly and peacefully entered Mecca itself, purging the Kaaba of its idols and declaring it a shrine to the one God, Allah. By the time Muhammad died in 632, most of Arabia had come under the control of this new Islamic state, and many had embraced the new faith.

Thus the birth of Islam differed sharply from that of Christianity. Jesus’ teaching about “giving to Caesar what is Caesar’s and to God what is God’s” reflected the minority and subordinate status of the Jews within the Roman Empire. Early Christians found themselves periodically persecuted by Roman authorities for more than three centuries, requiring them to work out some means of dealing with an often hostile state. The answer lay in the development of a separate church hierarchy and the concept of two coexisting authorities, one religious and one political, an arrangement that persisted even after the state became Christian.

The young Islamic community, by contrast, found itself constituted as a state, and soon a huge empire, at the very beginning of its history. Muhammad was not only a religious figure but also, unlike Jesus or the Buddha, a political and military leader able to implement his vision of an ideal Islamic society. Nor did Islam give rise to a separate religious organization, although tension between religious and political goals frequently generated conflict. No professional clergy mediating between God and humankind emerged within Islam. Teachers, religious scholars, prayer leaders, and judges within an Islamic legal system did not have the religious role that priests held within Christianity. No distinction between religious law and civil law, so important in the Christian world, existed within the realm of Islam. One law, known as the sharia (shah-REE-ah), regulated every aspect of life. The sharia (literally, “a path to water,” which is the source of life) evolved over the several centuries following the birth of this new religion and found expression in a number of separate schools of Islamic legal practice.

In little more than twenty years (610–632), a profound transformation had occurred in the Arabian Peninsula. What would subsequently become a new religion had been born, though it was one with roots in earlier Jewish, Christian, and Zoroastrian traditions. A new and vigorous state had emerged, bringing peace to the warring tribes of Arabia. Within that state, a distinctive society had begun to take shape, one that served ever after as a model for Islamic communities everywhere. In his farewell sermon, Muhammad described the outlines of this community: