﴿ وَمَآ ءَاتَيْنَٰهُم مِّن كُتُبٍۢ يَدْرُسُونَهَا ۖ وَمَآ أَرْسَلْنَآ إِلَيْهِمْ قَبْلَكَ مِن نَّذِيرٍۢ ﴾

“And yet, [O Muhammad,] never have We vouchsafed them any revelations which they could quote, and neither have We sent unto them any warner before thee.”

And We did not give them any scriptures for them to study nor did We send them any warner before you so on what grounds do they deny you?