Allah challenged the disbelievers in various parts of the Qur'an. For instance, Allah said in Surat Al-Qasas (28:49),
﴿قُلْ فَأْتُواْ بِكِتَـبٍ مِّنْ عِندِ اللَّهِ هُوَ أَهْدَى مِنْهُمَآ أَتَّبِعْهُ إِن كُنتُمْ صَـدِقِينَ ﴾
(Say (to them, O Muhammad ): "Then bring a Book from Allah, which is a better guide than these two (the Tawrah (Torah) and the Qur'an), that I may follow it, if you are truthful''). Also, Allah said in Surat Al-Isra' (17:88),
﴿قُل لَّئِنِ اجْتَمَعَتِ الإِنسُ وَالْجِنُّ عَلَى أَن يَأْتُواْ بِمِثْلِ هَـذَا الْقُرْءَانِ لاَ يَأْتُونَ بِمِثْلِهِ وَلَوْ كَانَ بَعْضُهُمْ لِبَعْضٍ ظَهِيرًا ﴾
(Say: "If mankind and the Jinn were together to produce the like of this Qur'an, they could not produce the like thereof, even if they helped one another.'') Allah said in Surat Hud (11:13),
﴿أَمْ يَقُولُونَ افْتَرَاهُ قُلْ فَأْتُواْ بِعَشْرِ سُوَرٍ مِّثْلِهِ مُفْتَرَيَاتٍ وَادْعُواْ مَنِ اسْتَطَعْتُمْ مِّن دُونِ اللَّهِ إِن كُنتُمْ صَـدِقِينَ ﴾
(Or they say, "He (Prophet Muhammad ) forged it (the Qur'an).'' Say: "Bring you then ten forged Surahs (chapters) like it, and call whomsoever you can, other than Allah (to your help), if you speak the truth!''), and in Surat Yunus (10:37-38),
﴿وَمَا كَانَ هَـذَا الْقُرْءَانُ أَن يُفْتَرَى مِن دُونِ اللَّهِ وَلَـكِن تَصْدِيقَ الَّذِى بَيْنَ يَدَيْهِ وَتَفْصِيلَ الْكِتَابِ لاَ رَيْبَ فِيهِ مِن رَّبِّ الْعَـلَمِينَ - أَمْ يَقُولُونَ افْتَرَاهُ قُلْ فَأْتُواْ بِسُورَةٍ مِّثْلِهِ وَادْعُواْ مَنِ اسْتَطَعْتُمْ مِّن دُونِ اللَّهِ إِن كُنتُمْ صَـدِقِينَ ﴾
(And this Qur'an is not such as could ever be produced by other than Allah (Lord of the heavens and the earth), but it is a confirmation of (the revelation) which was before it (i.e. the Tawrah, and the Injil), and a full explanation of the Book (i.e. Laws decreed for mankind) ـ wherein there is no doubt ـ from the Lord of all that exists.) (Or do they say: "He (Muhammad ) has forged it'' Say: "Bring then a Surah (chapter) like it, and call upon whomsoever you can besides Allah, if you are truthful!''). All of these Ayat were revealed in Makkah.
Allah also challenged the disbelievers in the Ayat that were revealed in Al-Madinah. In this Ayah, Allah said,
﴿وَإِن كُنتُمْ فِى رَيْبٍ﴾
(And if you (Arab pagans, Jews, and Christians) are in Rayb) meaning, doubt.
﴿مِّمَّا نَزَّلْنَا عَلَى عَبْدِنَا﴾
(Concerning that which We have sent down (i.e. the Qur'an) to Our servant) meaning, Muhammad ,
﴿فَأْتُواْ بِسُورَةٍ مِّن مِّثْلِهِ﴾
(then produce a Surah (chapter) the like thereof) meaning, similar to the Qur'an. This is the Tafsir of Mujahid, Qatadah, Ibn Jarir At-Tabari, Az-Zamakhshari and Ar-Razi. Ar-Razi said that this is the Tafsir of `Umar, Ibn Mas`ud, Ibn `Abbas, Al-Hasan Al-Basri and the majority of the scholars. And he gave preference to this view and mentioned the fact that Allah has challenged the disbelievers as individuals and as groups, whether literate or illiterate, thus making the challenge truly complete. This type of challenge is more daring than simply challenging the disbelievers who might not be literate or knowledgeable. This is why Allah said,
﴿فَأْتُواْ بِعَشْرِ سُوَرٍ مِّثْلِهِ﴾
(Bring you then ten forged Surahs (chapters) like it) (11:13), and,
﴿لاَ يَأْتُونَ بِمِثْلِهِ﴾
(They could not produce the like thereof) (17:88).
Therefore, this is a general challenge to the Arab disbelievers, the most eloquent among all nations. Allah challenged the Arab disbelievers both in Makkah and Al-Madinah several times, especially since they had tremendous hatred and enmity for the Prophet and his religion. Yet, they were unable to succeed in answering the challenge, and this is why Allah said,
﴿فَإِن لَّمْ تَفْعَلُواْ وَلَن تَفْعَلُواْ﴾
(But if you do it not, and you can never do it), indicating that they will never be able to answer the challenge. This is another miracle, in that, Allah clearly stated without doubt that the Qur'an will never be opposed or challenged by anything similar to it, for eternity. This is a true statement that has not been changed until the present and shall never change. How can anyone be able to produce something like the Qur'an, when the Qur'an is the Word of Allah Who created everything How can the words of the created ever be similar to the Words of the Creator