Both Christianity and Islam claim to be revealed religions. Jesus Christ (pbut) declared that the message he was delivering was not his but God's:
"I have not spoken of myself: but the Father which sent me, He gave me a commandment, what I should say, and what I should speak."
He described himself as
"A man that hath told you the truth, which I have heard of God"
In the same way it is claimed in the Qur'an that the Revelation which came to Prophet Muhammad (pbuh) was from the Lord of the worlds:
(And lo it (i.e., the Qur'an) is a Revelation of the Lord of the worlds, which the True Spirit hath brought down upon thy heart (O Muhammad), that thou mayest be one of the warners)
(Qur'an 26: 192-194)
From this it follows that the truth of either religions depends on the accuracy with which the inspired words of its Founder have been recorded and on the textual purity of its Scripture. If
the message which was revealed by God to a prophet has not reached us exactly as it was delivered, but has been misreported and altered, then to that extent that religion may be regarded as having deviated from truth. In this chapter we shall see how far the inspired words and Revelations of Jesus and Muhammad (pbut) have been faithfully recorded in the Gospels and the Qur'an respectively, and how far these Scriptures have remained free from alteration or interpolation of any kind.