Allāh, the Exalted, said:

وَإِن كُنتُمْ فِي رَيْبٍ مِّمَّا نَزَّلْنَا عَلَىٰ عَبْدِنَا فَأْتُوا بِسُورَةٍ مِّن مِّثْلِهِ وَادْعُوا شُهَدَاءَكُم مِّن دُونِ اللَّهِ إِن كُنتُمْ صَادِقِينَ ‎﴿٢٣﴾‏ فَإِن لَّمْ تَفْعَلُوا وَلَن تَفْعَلُوا فَاتَّقُوا النَّارَ الَّتِي وَقُودُهَا النَّاسُ وَالْحِجَارَةُ ۖ أُعِدَّتْ لِلْكَافِرِينَ ‎﴿٢٤﴾‏

“And if you (O unbelievers) are in doubt about (the truthfulness of) what We have sent down upon Our servant (Muḥammad), then produce a chapter of its like and call upon your witnesses (and your deities) besides Allāh (as your supporters and helpers in this endeavour), if you are truthful. But if you do not (bring a chapter of its like) — and you will never be able to do so (in the future) — then (declare your belief in Allāh, His Messenger and His Book and thereby) fear the Fire whose fuel is men and stones, (which is already created and) prepared for the disbelievers (in Allāh and His messengers).”
(Al-Baqarah, 2:23-24)

This is a rational argument evidencing the truthful nature of Allāh’s messenger (صلى الله عليه وسلم) and the correctness of his message. What is meant is, if you stubborn resisters of the messenger who reject his call and claim his untruthfulness are in any doubt or uncertainty concerning that which We have revealed onto Our servant (i.e., Prophet Muḥammad (صلى الله عليه وسلم) — as to whether it is true or not — then here lies a fair argument which will decide the matter between you and him. That argument is that he is but a man, just like you, not from another genus [of creation]. Ever since he grew up in your midst you have known that he was unlettered (i.e., did not read or write). Despite this however, he came to you with a Book, claiming it to be from Allāh, while you claim he has forged and invented it [as a lie against Allāh]. Therefore, if the matter is as you claim, bring forth a chapter of its like, and seek the assistance of all those you can find of helpers and witnesses. This matter must be especially easy for you [if what you claim is correct], considering you are a people possessing the most eloquent of speech and greatest of address, [while your desire to falsify the call of the Prophet (صلى الله عليه وسلم) is tremendous, as] you harbour the greatest of enmity towards him. Hence, if you bring forth a chapter of its like, the affair is as you have claimed [that Muḥammad (صلى الله عليه وسلم) forged the message], but if you do not do so and are instead utterly incapable of such — this would be indicative [that the Qurʾān is truly from Allāh] and a clear proof of the truthfulness of the Prophet (صلى الله عليه وسلم) and his message. It would then be incumbent upon you to follow him, thus protecting yourself from the fire [of Hell] whose heat has reached a degree that its fuel is men and stones, unlike the fire of this worldly life whose fuel is but firewood. This described fire [of Hell] is prepared for those who disbelieve in Allāh and His messenger. So, beware of disbelief in His messenger after it becomes evident to you that he is truly a messenger sent from Allāh.^[1]