The following words of the Qur'an will make this clear "And they say...

The following words of the Qur'an will make this clear "And they say: We will by no means believe in you, until you cause a spring of water to gush forth for us out of the earth, and you have a garden of palm-trees and vines, and you cause rivers to spring forth from the midst thereof in abundance; or you cause the heaven to fall down in pieces upon us, as you have given out, or you bring down God and the angels to vouch for you; or you have a house of gold, or you ascend by a ladder to heaven; neither will we believe your ascending there alone, until you cause a book to descend unto us, bearing witness of you which we may read.

Answer: My Lord be praised, Am I other than a man sent as an apostle?" [Qur'an 17.92-95]. Then again, "Nothing hindered us from sending you with miracles, except that the former nations have charged them with imposture" [Qur'an 17.61]. The thing by which we invited the people to believe in him, and with which he vied with them is the Qur'an.

For, says God, "Say, verily, if men and jinn were purposely assembled, that they might produce a book like this Qur'an, they could not produce one like unto it, although the one of them assigned the other" [Qur'an 17.90]. Then further, he says, "will they say, He hath forged the Qur'an? Answer, bring therefore ten chapters like unto it forged by yourself" [Qur'an 11.16].

This being the case the miracle of the Prophet with which he vied with the people and which he advanced as an argument for the truth of his claim to the prophetic mission, was the Qur'an. If it be said that this is quite clear, but how does it appear that the Qur'an is a mirage, and that it proves his prophecy, while just now we have proved the weakness of the proof of prophecy by means of miracles without any exceptions in the case of any prophet.

Besides, the people have differed in taking the Qur'an to be a miracle at all. For in their opinion one of the conditions of a miracle is that it should be quite different from any act which may have become habitual. But the Qur'an is of this sort, because it is only words, though it excels all created words. So it becomes a miracle by its superiority only, that is, the impossibility for people bringing anything like it, on account of its being highly eloquent.

This being the case, it differs from the habitual, not in genus but in details only, and that which differs in this way is of the same genus. Some people say that it is a miracle by itself, and not by its superiority.