The Qur’ân is the name given to Allah’s speech that He revealed to His servant and Messenger Muhammad (peace be upon him); speech that is recited as an act of worship, is miraculous, and cannot be imitated by man. It is the name of Allah’s Book, and no other book is called by this name.
The connection between the Creator and his Creation is by way of His Messengers, and these Messengers only know what Allah wants from them by way of revelation, either directly or indirectly. The rational mind cannot dismiss the possibility of revelation, since nothing is difficult for the all-powerful Creator
revelation is a communication between two beings: one that speaks, commands, and gives, and another who is addressed, commanded, and receives. Prophet Muhammad (peace be upon him) – as with every Prophet – never confused himself with the One who gave the revelation to him. As a human being, he felt his weakness before Allah, feared Allah’s wrath if he should disobey, and hoped for Allah’s mercy.
Proves why it is impossible that Mohammad (Pbuh) wrote the Quran :
1. No matter how brilliant or insightful a person might be, there is no way that he could discuss the happenings of nations lost to antiquity, issues of belief and Divine Law, the rewards and punishments of Heaven and Hell, and future events, all in such great detail without any contradiction and with a most perfect style and literary form. The Prophet (peace be upon him) had never once read a book nor met with any historian
2. The Qur’ân makes to the disbelievers a stern challenge that they will never be able to produce a chapter similar to it. Such a challenge would never have come from the Messenger (peace be upon him)
3. The Qur’ân, in some places, sternly rebukes Muhammad (peace be upon him) where he acted upon his own judgment in something and did not decide on what is best. The Qur’ân clarified the truth and showed the error of the Prophet (peace be upon him).
4. Many verses of the Qur’ân begin with the imperative verb “Say!” As a matter of fact, this occurs more than three hundred times, addressing Muhammad (peace be upon him) and directing him with respect to what he should say. He, thus, did not follow his own desires; he followed only what was revealed to him.
5. Complete harmony exists between what the Qur’ân says regarding the physical world and what has been discovered by modern science. This has been a source of amazement for a number of contemporary western researchers.
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Imanway
What Is Qur'an? ما هو القرآن 
