﴿ وَإِنَّ لَكُمْ فِى ٱلْأَنْعَٰمِ لَعِبْرَةًۭ ۖ نُّسْقِيكُم مِّمَّا فِى بُطُونِهِۦ مِنۢ بَيْنِ فَرْثٍۢ وَدَمٍۢ لَّبَنًا خَالِصًۭا سَآئِغًۭا لِّلشَّٰرِبِينَ ﴾

“And, behold, in the cattle [too] there is indeed a lesson for you: We give you to drink of that [fluid] which is [secreted from] within their bellies between that which is to be eliminated [from the animal's body] and [its] life-blood: milk pure and pleasant to those who drink it.”

Please check ayah 16:67 for complete tafsir.