The noble Koran is the book of God revealed by the angel Gabriel to prophet Mohammed (Blessings and peace of Allah be upon him), it is the word of God to his apostle (Blessings and peace of Allah be upon him) including everything a Muslim needs in his life, describing everything will happen to him in the hereafter, showing the great favors prepared for believers and the great torture prepared for disbelievers, the Koran is as God says:
“It is sent down by One Full of Wisdom, Worthy of all Praise (God)” Surat Fosselat, Verse 42.
The apostle (Blessings and peace of Allah be upon him) used to get it by revelation and when it was coming to him he felt a sentimental status seen by all people around him, after that he says the verses revealed to him by God, soon the people who could read and write amongst his companions receive them and write them down on pieces of leather or bones or stones and add them to each other according to his orders (Blessings and peace of Allah be upon him), following the instructions of Gabriel, he used to tell him the places of verses when revealed to him. He used to recite all revealed Koran upon him once a year in Ramadan, in the year he died he recited the whole Koran twice upon him in the month of Ramadan, this is among the secrets by which God protects His book.
Some people allege that Prophet Mohammed wrote the Koran by himself, this is a weak plea doesn’t depend on a single true evidence. The prophet was an illiterate man, he didn’t know how to read or write, he wasn’t educated in a university or by teachers, he only left Mecca twice to trade in Syria, he never gone to universities or to learn at nearby towns. Then how did he get the history of previous nations and the news of the following ages and these great legislations that astonish modern scientists as they match the modern actual life? How did he know the most recent scientific theories only discovered nowadays? How did he analyze the human soul and mentioned emotions and obsessions inside man whereas psychology and its theories only appeared at this time?
Many other things also assure that these words are the talk of The Creator and The All Powerful (God).