At the time Allah sent Muhammad—peace and blessings be upon him—people were of two sorts. They were either unlettered folk with no scripture at all, associating partners with the Most Merciful and bowing to idols; or they were People of the Scripture who had altered its meanings and rulings, tampered with its lawful and unlawful, and mingled its truth with falsehood—exactly as we see today. Were someone to ask those People of the Scripture to separate for him what the prophets had originally brought from the innovations introduced later, the great majority of them would be unable to do so; to them it has all merged into a single creed.

So Allah—blessed and exalted is He—sent Muhammad with the Book He revealed to him, confirming the Scripture that lay before it and protecting it. Through that Book He distinguished truth from falsehood, guidance from misguidance, and rectitude from deviation. The Exalted said:

“O People of the Scripture! Now there has come to you Our Messenger, making clear to you much of what you used to conceal from the Scripture, while overlooking much besides. There has come to you from Allah a light and a clear Book. Through it Allah guides those who seek His pleasure to the ways of peace, brings them out of darkness into light by His permission, and directs them to a straight path. They have indeed disbelieved who say, ‘Allah is the Messiah, son of Mary.’ Say: ‘Who holds any power against Allah if He wills to destroy the Messiah, son of Mary, his mother, and everyone on earth altogether?’ To Allah belongs the dominion of the heavens and the earth and whatever is between them; He creates what He wills, and Allah is capable of all things.” [5:15–17]