أَفَلا يَتَدَبَّرونَ القُرآنَ ۚ وَلَو كانَ مِن عِندِ غَيرِ اللَّهِ لَوَجَدوا فيهِ اختِلافًا كَثيرًا

Then do they not reflect upon the Qur'an? If it had been from [any] other than Allah, they would have found within it much contradiction.