"If the whole of mankind and jinns were to gather together to produce the like of this Quran, they could not produce the like of it, even if they backed up each other with help and support." [Quran, 17:88]
"This Quran is not such as can be produced by other than God but it is a confirmation (of revelations) before it, and a fuller explanation of the Book, wherein there is no doubt, from the Lord of the worlds. ; Do [the unbelievers] say, "[Muhammad] forged it"? Say, "Bring then a chapter like it and call (to your aid) whomsoever you can besides Allah, if you are truthful." [Quran, 10:37-38]
"Do they not consider the Quran with care? If it had been from other than God, they would have found in it a great deal of contradictions." [Quran, 04:82]