In any case, everyone agrees that when Allah sends a man and supports him with signs attesting to his veracity in what he conveys from Allah, then what he conveys can only be the truth. Otherwise, those very signs that prove his truthfulness would be proving the truthfulness of one who is not truthful, and it is impossible for definitive proofs to testify to falsehood.

The truthfulness established by the prophets’ signs and proofs means that his report from Allah corresponds exactly to what Allah revealed—neither contradicting it intentionally nor through error.

If someone were to object, saying, “I do not call an honest mistake a lie,” or, “The one who errs incurs no sin for his error,” we would reply: That argument is of no use here. The signs themselves show that Allah sent him to deliver His messages, and Allah does not commission someone whom He knows will report something contrary to what He said, just as it is impossible for Him to send someone who deliberately fabricates lies about Him. Indeed, even an ordinary person would never choose an emissary whom he knows will alter the message; if he knowingly appointed someone who would attribute to him what he never said, he would be ignorant and foolish, not knowledgeable and wise. How, then, could such a thing be ascribed to the All-Knowing of all knowers and the Wisest of all judges?

Moreover, the signs and proofs confirm his truthfulness in everything he conveys from Allah, and that Allah endorses him in all that he transmits. It is therefore impossible for him to be untruthful in any part of that message, and it is equally impossible for Allah to vouch for someone in every matter when that person is not truthful in every matter. Affirming the truthfulness of one who is not truthful is itself a lie, and lying is impossible for Allah.

Once it is clear that the one who proclaims himself to be Allah’s Messenger must be either a truthful messenger who