لَقَدْ كَانَ فِي قَصَصِهِمْ عِبْرَةٌ لِّأُولِي الْأَلْبَابِ ۗ مَا كَانَ حَدِيثًا يُفْتَرَىٰ وَلَٰكِن تَصْدِيقَ الَّذِي بَيْنَ يَدَيْهِ وَتَفْصِيلَ كُلِّ شَيْءٍ وَهُدًى وَرَحْمَةً لِّقَوْمٍ يُؤْمِنُونَ (111)
(12:111) There is an object lesson in these stories of the former people for those, who possess common sense. That thing which is being sent down in the Qur'an is not a forgery, but (is absolutely genuine and) it confirms the previous Scriptures, gives details *80 of everything, and is a guidance and blessing for the Believers.
*80) That is, "It gives details of everything that is required for the guidance of man. " Some people take "details of everything" to mean the details of everything in the world. So, when they do not find in it the details of mathematics, physics, medicine etc. etc. they become skeptical. Whereas the Qur'an claims to give the details of only one `subject', "Guidance", for which it has been sent down, and it does give the details of everything that is essential for it.