Let’s think about it. If Prophet Muhammad really made up the Quran to promote himself, he would have used it for his own benefit. But in some cases, it happened that the Quran comes with what is against the opinion of Prophet Muhammad, and sometimes the revelation comes too late to judge a severe problem in the Islamic society to test the Muslims although it could have come from day one and end the case.
If someone came and charge a great king’s wife with adultery, then some people began to believe this man and began to talk about that. This king has the media with him and can easily say that this man is a liar and knows that people shall believe the king’s media. Shall the king who loves his wife more than anyone else use the media and say that this man is a liar? This happened with Prophet Muhammad. Prophet Muhammad spent a month suffering till the Quran was sent down from God and said that this man was a liar. If Prophet Muhammad was the one who made up the Quran, he would have made up some verses from day one telling that this man is a liar. He won’t have spent one month in torture and agony if he really had the tool to end this up.
The Quran talks about the stories of the prophets of God from Adam to Jesus. It gives legislations in different aspects of life from politics to economy to social affairs to heritage laws which are actually miraculous as the Quran covers all the heritage problems in only 4 versest only that, but some scientific facts recently discovered were actually written in the Quran 1400 years ago. http://quranteachersheffield.co.uk/
Prophet Muhammad was never concerned with poetry. He never wrote a book as he was illiterate. He was never concerned with the beliefs of Jews and Christians. He was well-known by his honesty and good morals that all his tribe used to call him the truthful and the honest. Then suddenly when he is forty years old he comes with highly rhetorical verses that astonished Arabs who were well-known by having high rhetorical sense. Isn’t that worth pondering? The Quran even challenges Arabs and all people afterwards to write a chapter like a chapter in the Quran. This challenge hasn’t been met for 1400 years.