Dale T. Irvin & Scott W. Sunquist, History of the World Christian Movement, Vol 1: Earliest Christianity to 1453. Maryknoll, New York: Orbis Books, 2006, pp. 234-41.
Muhammad (570-632 C.E.)
Born into the ruling tribe of Quraysh in Arabia (a tribe that claimed to trace its lineage to Ishmael) and after traveling with his uncle Abu Talib on caravans and being exposed to various forms of paganism and idolatry (while his business was prospering), Muhammad began to receive direct revelations from the angel Gabriel in 610 C.E. that he would begin to preach and that would also eventually become the content of the Qur’an. The basic message was a call to turn away from paganism and idolatry and begin to worship the one true God of Abraham, who was Allah.
When his message was seen as a threat, he fled Mecca (once seeking refuge in Ethiopia, and once in Medina) and gathered political and military support to defend the Muslim religion, a move that culminated in a new monotheistic political state that would spread far beyond the Arabian desert over the next century. Since the revelations Muhammad received instructed him to exterminate polytheism and idolatry, he forced the people to either worship the one true God or face extinction (his policy, however was to spare monotheistic Jews, Christians, Zoroastrians and Sabeans).
In addition to the five pillars of Islam (reciting the shahada, seven prayers a day facing Mecca instead of Jerusalem, almsgiving, fasting from sunup to sundown in the month of Ramadan, and making a pilgrimage to Mecca during one’s lifetime), Muhammad also engaged in polemics against the central Christian beliefs about God (that Jesus was God, that Jesus was crucified, that God has a son, that God is three persons, etc.). Therefore, although Muhammad did not execute Christians automatically but granted them the status of dhimmi (“protected people”) and let them practice their religion, he forced a heavy tax on Christian communities, forbid them from proselytizing (sharing their faith), and began the slow process of taking over much of the previously Christian “worship space” (e.g. building mosques that dominated the cultural landscape in previously Christian dominated areas).
Muhammad’s aggressive promotion of Islam and his political success enabled him to unite Arabia and set a precedence of expansion that would lead to the first ever great historical decline of Christianity.