From HERE:
Dr. Samuel M. Zwemer, who in a very real sense can be referred to as "the apostle to the Mohammedan world," calls attention to the strange parallel between the Reformation in Europe under Calvin and that in Arabia under Mohammed. Says he: "Islam is indeed in many respects the Calvinism of the Orient. It, too, was a call to acknowledge the sovereignty of God's will. 'There is no god but God.' It, too, saw in nature and sought in revelation the majesty of God's presence and power, and manifestations of His glory, transcendent and omnipotent. 'God,' says Mohammed, 'there is no god but He, the living, the self-subsistent, slumber seizeth Him not, nor sleep—His throne embraceth the heavens and the earth and none can intercede with Him save by His permission. He alone is exalted and great' . . . . It is this vital theistic principle that explains the victory of Islam over the weak divided and idolatrous Christendom of the Orient in the sixth century. . . . The Message of Mohammed, when he first unfurled the green banner, 'There is no god but God; God is king, and you must and shall obey His will,' was one of the simplest accounts ever offered of the nature of God and His relation to man. . . . This was Islam, as it was offered at the sword's point to people who had lost the power of understanding any other argument."
