Constantly the Quran points out that Muhammad had not come to cancel the older religions, to contradict their prophets or to start a new faith. His message is the same as that of Abraham, Moses, David, Solomon, or Jesus. The Quran mentions only those prophets who were known to the Arabs, but today Muslim scholars argue that had Muhammad known about the Buddhists or the Hindus, the Australian Aborigines or the Native Americans, the Quran would have endorsed their sages, too, because all rightly guided religion that submitted wholly to God, refused to worship man-made deities, and preached justice and equality came from the same divine source. Hence Muhammad never asked Jews or Christians to accept Islam, unless they particularly wished to do so, because they had received perfectly valid revelations of their own.

Karen Armstrong, Islam