An-Nu'mân ibn Bashîr narrated that he heard Allah's Messenger , saying, "Both. lawful (Halál) and prohibited things (Harán) are evident but in between them there are doubtful things' and most people have no knowledge about them. So he who saves himself from these doubtful things, saves his religion and his honor (i.e. keeps them blameless). And he who indulges in these doubtful things is like a shepherd who pastures (his animals) near the Himi (private pasture) of someone else and at any moment he is liable to get in it. (Opeople!) Beware. Every king has a Himi and the Himi of Allah on the earth is what He declared prohibited (Harim). Beware. In the body there is a piece of flesh if it becomes sound and healthy the whole body becomes sound and healthy but if it gets corrupt the whole body gets corrupt and that is the heart.”
In this hadith, we note once again one of the scientific signs in the Sunnah of the Prophet . It is well known that any disease, which affects the heart causing any kind of damage or harm to it, will consequently affect the whole body. This is due to the fact that the right side of the heart pumps oxygen-poor blood to the lungs for new oxygen; the left side of the heart receives oxygen-rich blood from the lungs and pumps it to the body through the arteries.
This blood provides trillions of body cells with oxygen and nutrition. If this process undergoes any form of disorder or malfunction, this will consequently affect all the body cells.
One cannot help wondering when he reads this hadith of the Prophet; that critically describes this fact;
"In the body there is a piece offlesh if it becomes sound and healthy the whole body becomes sound and healthy but if it gets corrupt the whole body gets corrupt and that is the heart.'
This is a medical fact that was only discovered when Ibn an-Nafis' discovered minor blood circulation (pulmonary circulation) in the 7" century A.H. (13" century A.C.). This discovery remained concealed and neglected for more than three centuries, until some westerners tried to claim its discovery, and attribute the idea to themselves, so they revived it, and tried to develop the initial theory by adding some of their own thoughts. It is now proven scientifically that if the heart is healthy, the Circulatory System will be in a perfect condition, and hence the whole body will be sound and healthy. On the contrary, if the heart malfunctions, the whole body will be disturbed, due to the circulatory disorder.
This fact raises an important question: Who taught this illiterate Messenger is all this except Allah, the Creator? Who at that time (more than 1400 years ago) in the Arabian Peninsula could perceive how the human circulatory system functions and comprehend the role of the heart in this process? No source of knowledge could attain this but Divine Revelation. The Prophet g would not examine such a scientific fact unless he was quite sure of its validity and the Truthfulness of its Source.
The above argument is mainly relevant to the bodily organ called “the heart'; that pear-shaped muscular organ located behind the lower part of the breastbone, which is no bigger than the palm of your hand in size and does not exceed 1/3 of a kg, in weight, in an average adult. This heart pulsates at a rate of almost seventy beats per minute, which comes to almost 100,000 beats per day. It pumps five liters ofblood per minute, 7,200 liters per day through a complex net of veins, arteries and blood capillaries, which reach up to thousands of kilometers in length to be able to transfer the oxygen-rich blood to every cell throughout the body, while removing the oxygen-poor blood from them.
It is a well known fact now, that if the heart is healthy, the Circulatory System will run perfectly and each living cell will receive its share of blood that carries nutrition and oxygen to it, which in turn burns the nutrients hence, releasing energy. However, if the heart starts to malfunction, Circulatory System of the blood will consequently be disturbed. Moreover, insufficient amounts of oxygen and nutrients will reach the blood cells leading to a total bodily disturbance.
Nevertheless, the heart has many different implications and connotations in the Glorious Qur’an, the Sunnah of the Prophet is, and even in human perception that goes beyond this piece of flesh located within the chest and propels blood through the arteries. These connotations and implications are related to human emotions, concepts, ideas, thoughts, beliefs, and morals as well as to their behavioral control. These are not located inside the muscular heart, even though they are still related to it in a way, which has not yet been perceived by man. Some scholars such as Imam al-Ghazali' perceived the heart as a moral entity or a Divine spiritual fine entity, which has a certain link to this physical organ, in a way which is not perceptible.
Imam al-Ghazali believes that this moral heart is the reality of man. It is this intellectual entity of the human being which rationalizes, perceives and gains knowledge and it is the part of the human being which is addressed (by Allah), punished, blamed and ordered, etc... This moral heart or Divine entity is linked to the true meaning and reality of the soul, which is an ever-closed secret
Here again we come across one of the scientific signs in the hadith of the Prophet is. If the center of emotions, concepts, thoughts, beliefs and morals functions properly, the whole reality of that man (i.e. his soul and spirit) that rationalizes, conceives, feels, etc. will function properly and if it becomes corrupt, man's whole life will be disturbed.
The scientific sign in this hadith is evident whether we interpret it according to its concrete, material and organic side i.e. the muscular heart or according to its abstract, moral and spiritual side i.e. the unseen aspect. From whichever aspect you look at it, you realize that it is perfectly true, accurate and comprehensive.
The human body totally depends on this muscular organ called “the heart” in order to function properly, and as mentioned earlier, if it malfunctions, then the whole body will be affected. The same applies to the heart in its moral immaterial sense, which is the source of emotions, beliefs, concepts, thoughts, morals and ethics. If this moral heart is sound and healthy, all of these moral aspects will be sound which means that the whole human body will then be perfect and healthy.
The illiterate Prophet is would not discuss this scientific fact unless he was quite sure of the Truthfulness of its Source. There is no room for doubt that he was supported by Allah's Ultimate Knowledge that goes beyond the Prophet's time and knows that someday man will be able to realize such facts. Thus, these scientific signs constitute a concrete proof of the Prophet's truthfulness and the veracity of his message.