Al-Jawāb as-Sahīh li-man baddala dīn al-Masīh - Ibn Taimiya - (5/424)

So He demanded of them that they bring ten surahs comparable to it—all of them concocted—together with everyone they could enlist besides Allah. Then He reduced the challenge to a single surah, they and whomever they could summon.

He said:
“If they do not respond to you, then know that it has been sent down with the knowledge of Allah, and that there is no deity but Him.” ⦗Hūd 14⦘

This, in fact, is the very core of his message: the testimony that there is no deity except Allah and the testimony that Muhammad is the Messenger of Allah.

The Exalted also said:
“If they do not respond to you, then know that it has been sent down with the knowledge of Allah.” ⦗Hūd 14⦘

And He said:
“Yet Allah bears witness to what He has sent down to you; He sent it down with His knowledge, and the angels likewise bear witness.” ⦗al-Nisāʾ 166⦘

That is to say: He knows it to be revealed, not fabricated, just as He says:
“This Qur’an could never have been produced by anyone other than Allah.” ⦗Yūnus 37⦘

فَطَلَبَ مِنْهُمْ أَنْ يَأْتُوا بِعَشْرِ سُوَرٍ مِثْلِهِ مُفْتَرِيَاتٍ هُمْ وَكُلُّ مَنِ اسْتَطَاعُوا مَنْ دُونِ اللَّهِ، ثُمَّ تَحَدَّاهُمْ بِسُورَةٍ وَاحِدَةٍ هُمْ وَمَنِ اسْتَطَاعُوا، قَالَ: {فَإِنْ لَمْ يَسْتَجِيبُوا لَكُمْ فَاعْلَمُوا أَنَّمَا أُنْزِلَ بِعِلْمِ اللَّهِ وَأَنْ لَا إِلَهَ إِلَّا هُوَ} [هود: ١٤] . وَهَذَا أَصْلُ دَعْوَتِهِ، وَهُوَ الشَّهَادَةُ بِأَنَّهُ لَا إِلَهَ إِلَّا اللَّهُ، وَالشَّهَادَةُ بِأَنَّ مُحَمَّدًا رَسُولُ اللَّهِ. وَقَالَ تَعَالَى: {فَإِنْ لَمْ يَسْتَجِيبُوا لَكُمْ فَاعْلَمُوا أَنَّمَا أُنْزِلَ بِعِلْمِ اللَّهِ} [هود: ١٤] . كَمَا قَالَ: {لَكِنِ اللَّهُ يَشْهَدُ بِمَا أَنْزَلَ إِلَيْكَ أَنْزَلَهُ بِعِلْمِهِ وَالْمَلَائِكَةُ يَشْهَدُونَ} [النساء: ١٦٦] . أَيْ: هُوَ يَعْلَمُ أَنَّهُ مُنَزَّلٌ، لَا يَعْلَمُ أَنَّهُ مُفْتَرًى، كَمَا قَالَ: {وَمَا كَانَ هَذَا الْقُرْآنُ أَنْ يُفْتَرَى مِنْ دُونِ اللَّهِ} [يونس: ٣٧] .