وَإِنَّ لَكُمْ فِي الْأَنْعَامِ لَعِبْرَةً ۖ نُّسْقِيكُم مِّمَّا فِي بُطُونِهِ مِن بَيْنِ فَرْثٍ وَدَمٍ لَّبَنًا خَالِصًا سَائِغًا لِّلشَّارِبِينَ (66)
(16:66) And surely there is a lesson for you in the cattle: We give you to drink of that which is in their bellies between filth and blood, that is, pure milk, *54 which is very pleasant to those who drink it.
*54) "....between filth and blood......":This refers to the most wonderful process of the formation of pure milk in the bellies of the she-cattle, for, the fodder they eat turns into blood, filth and pure milk, which is altogether different from the first two in its nature, colour and usefulness. Some she-cattle produce milk in such abundance that after suckling their young-ones a large quantity of it is left to make excellent human food.