Allah tells us about the foolishness of the disbelievers' ignorant minds, when they said about the Qur'an:
إِنْ هَـذَا إِلاَّ إِفْكٌ
(This is nothing but a lie), meaning an untruth.
افْتَرَاهُ
(that he has invented,) meaning the Prophet .
وَأَعَانَهُ عَلَيْهِ قَوْمٌ ءَاخَرُونَ
(and others have helped him in it.) means, he asked other people to help him compile it. So Allah said:
فَقَدْ جَآءُوا ظُلْماً وَزُوراً
(In fact, they have produced an unjust wrong and a lie.) meaning, they are the ones who are telling a lie, and they know that it is false, for their own souls know that what they are claiming is not true.
From this point onward the objections raised by infidels and polytheists against the Holy Qur'an and the prophethood of the Holy Prophet ﷺ are related together with the answers to those objections.
The first objection was that the Qur'an was not a revealed book from Allah Ta’ ala, but has been compiled from the old stories and narrations by the Jews and Christians which have been reduced into writing by the Companions of the Holy Prophet ﷺ ، since he himself was illiterate and could not write. And because he could not read or write, he would get them read out to him day and night, so that he could remember them by heart, then he would repeat them before people and claim that he had received that revelation from Allah Ta’ ala.
The answer to this objection was given by the Holy Qur’ an قُلْ أَنزَلَهُ الَّذِي يَعْلَمُ السِّرَّ فِي السَّمَاوَاتِ وَالْأَرْضِ , that is (Say, "It is sent down by the One who knows the secret in the heavens and the earth - 25:6).
The essence of this answer is that the Qur'an itself is an evidence to the fact that it is the Divine message from Him who is Omniscient and who knows fully well all the secrets of the Heavens and the earth. This is why Qur'an is a miraculous Message, and the whole world is challenged to bring out a Surah or even a verse to match it, if its divine origin is refused. This was a challenge to a people - the Arabs - who were well known for their literary proficiency and art of expression, and for whom composition of a piece of literature was not a problem. But they too did not dare to attempt to compose something similar to Qur’ an. Although they were willing to sacrifice all their material wealth for opposing the Holy Prophet ﷺ in his mission, so much so that they were willing to sacrifice even their children and their own lives to counter the Holy Prophet ﷺ mission and message, but they dared not attempt to compose a passage similar to a Surah of the Qur'an.
This is a clear proof of the fact that it is not a work of a human being. Otherwise other people could also have composed passages similar to Qur'an. Therefore, it is definitely the revelation from Allah Ta ala. Apart from the beauty of expression and language, the Book also excels in its meanings. The multifarious subjects it covers can only be dealt by One who knows everything whether hidden or exposed. This subject has been dealt with in detail in the first volume of Ma’ ariful Qur'an.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 6–8
Those who denied the truth used to denigrate the Quran as a false testament, but in fact the target of their allegation was the Prophet Muhammad. The Prophet appeared to them as an ordinary man. They were unable to understand how an ordinary man could be the possessor of an extraordinary Book. The Quran touches upon various topics of a historical, psychological and social nature, etc., but no factual error has ever been pointed out in it. This proves that the Quran was authored by a Being who is aware of the secrets of the universe to the fullest extent. Had it not been so, the Quran also would have been full of mistakes—as are found in other man-made books. This fact in itself is the greatest argument in favour of the Quran being a Book of God. Those who make baseless statements against the Quran, are indulging in undue bravado. Such people will definitely be seized upon by God. However, if they come back to the right path, it is not God’s way to take revenge after their repentance. God looks at the individual’s present and not his past.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.