Stomach

Ibn Rajab رحمه الله said: "The diet is the foundation of medicine and the stomach is the foundation of illness."

Ibn Qayyim رحمه لله said in Medicine of the Prophet ﷺ

"Material illnesses arise from an increase of matter which comes to a point of excess in the body whereby it harms its natural functions – and these are the most common illnesses. They are caused by consuming more food before the previous meal has been properly digested; by eating in excess of the amount needed by the body; by consuming food which is of little nutritional value and is slow to digest; and by eating different foods which are complex in their composition. So when a person fills his belly with these foods and it becomes a habit, they cause him various diseases.

“When a person is moderate in his eating and takes only so much of it as he needs, keeping a balance of quantity and quality, the body benefits more from this than it does from a large amount of food. There are three degrees of eating: (1) out of need; (2) in moderation; and (3) in excess.

“The Prophet ﷺ has made it known that he found sufficient such morsels as would keep his spine upright, with which his strength would not be lowered or weakened; but if one goes beyond that, then let him eat to fill a third of his belly, and leave another third for water and a third for breath. This is most useful for body and heart. For if the belly is filled with food, it does not have enough space for drink, and when drink is added to it, this leaves little space for breath. Thus it is afflicted by distress and fatigue, and it bears this like one carrying a heavy burden – and this state will lead to corruption of the heart; and the limbs become too lazy to perform the obligations, and instead they move swiftly in submission to desires brought about by fullness of the belly."