The Qur’aan was revealed 600 years before the Muslim scientist Ibn Nafees
described the circulation of the blood and 1,000 years before William Harwey
brought this understanding to the Western world. Roughly thirteen centuries
before it was known what happens in the intestines to ensure that organs are
nourished by the process of digestive absorption, a verse in the Qur’aan
described the source of the constituents of milk, in conformity with these
To understand the Qur’aanic verse concerning the above concepts, it is
important to know that chemical reactions occur in the intestines and that,
from there, substances extracted from food pass into the blood stream via a
complex system; sometimes by way of the liver, depending on their chemical
nature. The blood transports them to all the organs of the body, among which
are the milk-producing mammary glands.
In simple terms, certain substances from the contents of the intestines enter
into the vessels of the intestinal wall itself, and these substances are
transported by the blood stream to the various organs.
This concept must be fully appreciated if we wish to understand the following
verse in the Qur’aan: “And verily in cattle there is A lesson for you. We
give you to drink Of what is inside their bodies, Coming from a
conjunction Between the contents of the Intestine and the blood, A milk
pure and pleasant for Those who drink it.” [Al-Qur’aan 16:66] 
“And in cattle (too) ye Have an instructive example: From within their
bodies We produce (milk) for you To drink; there are, in them, (Besides),numerous (other) Benefits for you; And of their (meat) ye eat.” [Al-Qur’aan 23:21]
The Qur’aanic description of the production of milk in cattle is strikingly
similar to what modern physiology has discovered.