1400 years ago people thought that milk came from the white fat near the nipples. However today this turned out to be false. Milk is produced in mammary glands which in turn get the nutrients directly from the blood stream. The blood stream gets it nutrients from the digestive system.
٦٦ وَإِنَّ لَكُمْ فِي الْأَنْعَامِ لَعِبْرَةً ۖ نُسْقِيكُمْ مِمَّا فِي بُطُونِهِ مِنْ بَيْنِ فَرْثٍ وَدَمٍ لَبَنًا خَالِصًا سَائِغًا لِلشَّارِبِينَ
"We give you drink, from their bellies digested food and blood". No mistakes in the Quran.
How could an illiterate man who lived 1400 years ago have known where milk comes from?
The Quran (Koran, the book of Islam) contains scientific knowledge that could not have been known 1400 years ago. It ranges from basic arithmetics to the most advanced topics in astrophysics. You are invited to go through those miracles and judge for yourself.