The cornerstone of the Prophetic mission was to preach Divine Unity. All Prophets concentrated on this basic principle: O my people, serve God: You have no god other than He (11:84).

God has sent at least one Prophet to every people. The fact that all of them, regardless of time or place, agree on one basic principle shows that they did not speak or act on their own; rather, they did no more than teach the Message received from God. Philosophers and thinkers, no matter how great they may be, disagree among themselves because they depend on their own intellect and findings. Frequently, the same philosophical or sociological school contains different opinions.

Such a development was unknown among the Prophets, further evidence that they were taught by a Single, Eternal Teacher—God—and not guided by defective human reasoning. Such a unity of belief is also a strong evidence of Divine Unity, the fundamental principle of their mission, as declared by Muhammad: "The most meritorious of the words spoken by me and the Prophets before me is: 'There is no god but God, He is One, having no partners.'" [1]