Obstinance of the Chiefs of the Quraysh
Allah tells;
وإذا تتلى عليهم آياتنا بينات قال الذين ﻻ يرجون لقاءنا ايت بقرآن غير هذا أو بدله
And when Our clear Ayat are recited unto them, those who hope not for their meeting with Us, say: "Bring us a Qur'an other than this, or change it.''
Allah tells us about the obstinance of the disbelievers of the Quraysh, who were opposed to the message and denied Allah. When the Messenger read to them from the Book of Allah and His clear evidence they said to him: "Bring a Qur'an other than this.'' They wanted the Prophet to take back this Book and bring them another book of a different style or change it to a different form. So Allah said to His Prophet:
قل ما يكون لي أن أبدله من تلقاء نفسي
Say: "It is not for me to change it on my own accord;
This means that it is not up to me to do such a thing. I am but a servant who receives commands. I am a Messenger conveying from Allah.
إن أتبع إﻻ ما يوحى إلي إني أخاف إن عصيت ربي عذاب يوم عظيم
I only follow that which is revealed unto me. Verily, I fear the torment of the Great Day (the Day of Resurrection) if I were to disobey my Lord.
The Evidence of the Truthfulness of the Qur'an
Muhammad (peace be upon him) then argued with supporting evidence to the truthfulness of what he had brought them:
Allah tells;