Because of humanity's moral weakness, God has sent prophets to teach both individuals and nations correct moral and spiritual behavior. After creation and sustenance, God's mercy is consummated in these acts of divine guidance. Although right and wrong are inscribed in the human heart, the inability or refusal of many people to decipher that inscription has made prophetic guidance necessary. Religions are, therefore, basically one, even though their institutionalized forms may differ. Prophets are one indivisible unity, and one must believe in all of them, for to accept some and reject others amounts to a denial of the divine truth.
Some prophets are superior to others, however, particularly in steadfastness under trial.
From this arises the Islamic belief that prophethood was consummated and finished with him and that the Qur'an is the final and most nearly perfect revelation of God, consummating and superseding all earlier ones. The divine activities of creation, sustenance, and guidance end with the final act of judgment. On the Day of Judgment, all humanity will be gathered, and individuals will be judged solely according to their deeds. Besides the Last Judgment, which will be on individuals, the Qur'an recognizes another kind of divine judgment, which is meted out in history to nations, peoples, and communities. Nations, like individuals, may be corrupted by wealth, power, and pride, and, unless they reform, these nations are punished by being destroyed or subjugated by more virtuous nations.