فَلَعَلَّكَ تَارِكُۢ بَعۡضَ مَا يُوحَىٰٓ إِلَيۡكَ وَضَآئِقُۢ بِهِۦ صَدۡرُكَ أَن يَقُولُواْ لَوۡلَآ أُنزِلَ عَلَيۡهِ كَنزٌ أَوۡ جَآءَ مَعَهُۥ مَلَكٌۚ إِنَّمَآ أَنتَ نَذِيرٞۚ وَٱللَّهُ عَلَىٰ كُلِّ شَيۡءٖ وَكِيلٌ
So perchance you (Muhammad SAW) may give up a part of what is revealed unto you, and that your breast feels straitened for it because they say, "Why has not a treasure been sent down unto him, or an angel has come with him?" But you are only a warner. And Allah is a Wakil (Disposer of affairs, Trustee, Guardian, etc.) over all things.
أَمۡ يَقُولُونَ ٱفۡتَرَىٰهُۖ قُلۡ فَأۡتُواْ بِعَشۡرِ سُوَرٖ مِّثۡلِهِۦ مُفۡتَرَيَٰتٖ وَٱدۡعُواْ مَنِ ٱسۡتَطَعۡتُم مِّن دُونِ ٱللَّهِ إِن كُنتُمۡ صَٰدِقِينَ
Or they say, "He (Prophet Muhammad SAW) forged it (the Quran)." Say: "Bring you then ten forged Surah (chapters) like unto it, and call whomsoever you can, other than Allah (to your help), if you speak the truth!"
فَإِلَّمۡ يَسۡتَجِيبُواْ لَكُمۡ فَٱعۡلَمُوٓاْ أَنَّمَآ أُنزِلَ بِعِلۡمِ ٱللَّهِ وَأَن لَّآ إِلَٰهَ إِلَّا هُوَۖ فَهَلۡ أَنتُم مُّسۡلِمُونَ
If then they answer you not, know then that the Revelation (this Quran) is sent down with the Knowledge of Allah and that La ilaha illa Huwa: (none has the right to be worshipped but He)! Will you then be Muslims (those who submit to Islam)?