Michael H. Hart's Testimony
"My choice of Muhammad to lead the list of the world's most influential persons may surprise some readers and may be questioned by others, but he was the only man in history who was supremely successful on both the religious and secular levels." "Of humble origins, Muhammad founded and promulgated one of the world's great religions, and became an immensely effective political leader. Today, thirteen centuries after his death, his influence is still powerful and pervasive."
Reference : 100, a Ranking of the Most Influential Persons in History