That a man or group of men saw the united cultures of the Jews and Christians around them and realized their own societies could be united by leveraging the religious foundations of the Jews and Christians.
This is strikingly evident in the way the Qur’an appeals to and leans on Jewish and Christian scriptures but only in so far as the audience is not encouraged to adopt those faiths.
Another big tell is the way in which the Qur’an frequently responds to its audience’s reception, as if each new surah was given to the people, their criticisms heard, and then new surahs were ‘received’ to override or smooth over any critiques with new revelation from God.
One other giveaway is the alteration of long-established historical events in Jewish and Christian history such as the way the stories of Mary and Elizabeth are retold, among others.
Jesus, whom the Qur’an holds up as a prophet, said this:
“Beware of the false prophets, who come to you in sheep’s clothing, but inwardly are ravenous wolves. You will know them by their fruits. Are grapes gathered from thorn bushes or figs from thistles? Even so, every good tree bears good fruit, but the bad tree bears bad fruit. A good tree cannot bear bad fruit, nor can a bad tree bear good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. So then, you will know them by their fruits.”
-Matthew 7:15-20
The Apostle Paul said this:
“I marvel that you are so quickly deserting Him who called you by the grace of Christ for a different gospel, which is really not another, only there are some who are disturbing you and want to distort the gospel of Christ. But even if we, or an angel from heaven, should proclaim to you a gospel contrary to the gospel we have proclaimed to you, let him be accursed! As we have said before, so I say again now, if any man is proclaiming to you a gospel contrary to what you received, let him be accursed! “
-Galatians 1:6-9
The Qur’an comes almost 600 years after Christ and was ‘received’ from the Angel Gabriel.
“But even if we, or an angel from heaven, should proclaim to you a gospel contrary to the gospel we have proclaimed to you, let him be accursed!”
Jesus said:
“Many false prophets will arise and will deceive many. And because lawlessness is multiplied, most people’s love will grow cold. But the one who endures to the end, he will be saved. And this gospel of the kingdom shall be proclaimed in the whole world as a witness to all the nations, and then the end will come.”
-Matthew 24:11-14
Agreeing with Apostle Paul and inspired by the revelation he has received, Apostle John writes:
“I bear witness to everyone who hears the words of the prophecy of this book: If anyone adds to them, God will add to him the plagues which are written in this book.
And if anyone takes away from the words of the book of this prophecy, God will take away his part from the tree of life and from the holy city, which are written in this book.
He who bears witness to these things says, “Yes, I am coming quickly.” Amen. Come, Lord Jesus.
The grace of the Lord Jesus be with all. Amen.”
-Revelation 22:18-21