Do they say, ‘He has forged this (Quran)?’ Say (to them in reply), ‘If you are truthful (in your objection then) bring ten forged chapters like it, calling upon whom you can (for your help) apart from Allah.’ (5:89) 
Commentary
NUMBER 10: When Muslims say that the Quran is a miracle, is it not only from the point of view of the eloquence and beauty of its composition – this is only one aspect of the miraculous nature of this Book. In addition, because of the profundity of the teachings, the beauty in its admonitions, the logical and scientific proofs which it brings forth, the knowledge of ‘the unseen’ which it recounts to us, and the amazing usage of the rules of Arabic grammar, plus so much more - all make this Book truly stand out from anything else. 
Since the beginning of its revelation to the heart of the Prophet ] - until today, although a few people have tried, they all failed miserably in creating  something “like” the Quran. 
The Quran even challenges humanity and jinn to work with one another to bring something “like” it, but still 1,453 years have passed and this challenge has remained unanswered. 
In some places in the Quran, the world of creation is challenged to bring the like of this Heavenly Book: 
قُلْ لَئِنِ اجْتَمَعَتِ الْإِنْسُ وَالْجِنُّ عَلَى أَنْ يَأْتُوا بِمِثْلِ هَذَا الْقُرْآنِ لَا يَأْتُونَ بِمِثْلِهِ وَلَوْ كَانَ بَعْضُهُمْ لِبَعْضٍ ظَهِيرًا٨٨ 
Say, “If mankind and jinn gathered in order to produce the like of this Quran, they can not produce the like of it, even if they were to be each others’ assistants.” (17:88)
The challenge is then reduced and we are asked to bring ten chapters like that which are in the Quran: 
أَمْ يَقُولُونَ افْتَرَاهُ قُلْ فَأْتُوا بِعَشْرِ سُوَرٍ مِثْلِهِ مُفْتَرَيَاتٍ وَادْعُوا مَنِ اسْتَطَعْتُمْ مِنْ دُونِ اللَّهِ إِنْ كُنْتُمْ صَادِقِينَ١٣ 
Or do they say, “He invented it”? Say, “Then bring ten surahs like it that have been invented and call upon [for assistance] whomsoever you can besides Allah, if you should be truthful.” (11:13)
Even this is further lessened and we are told to bring one chapter like the Quran:
وَإِنْ كُنْتُمْ فِي رَيْبٍ مِمَّا نَزَّلْنَا عَلَى عَبْدِنَا فَأْتُوا بِسُورَةٍ مِنْ مِثْلِهِ وَادْعُوا شُهَدَاءَكُمْ مِنْ دُونِ اللَّهِ إِنْ كُنْتُمْ صَادِقِينَ٢٣ 
And if you are in doubt about what We have sent down upon Our Servant [Muḥammad], then produce a surah the like thereof, and call upon your witnesses other than Allah, if you are truthful. (2:23)
Keeping in mind the shortest chapters of the Quran such as al-Kawthar or al-Naṣr have no more than 3 verses and only a handful or words, it should not be hard to take Allah up on His challenge, but until today, no one has managed to do this…
Point of Reflection
If this Quran was the work of a ‘regular human being’ and the Prophet “copied it” from previous scriptures, then why is it that for the past 1,453 years - NONE of the opponents of Islam have been able to produce even ONE chapter “like” the Quran to respond to its challenge?