What Shaykh al-Islam mentioned—namely, fearing harm and indigestion—differs from that which is harmful in itself. Here, the harm lies in excess: the food is not harmful in itself, but consuming too much of it becomes harmful and distressing. Indeed, even if a person does not perceive any harm, it appears to me, from a medical standpoint, that he is harmed, because when one fills the stomach, it will suffer and become fatigued.

Is the evil referred to in the Prophet’s saying, peace and blessings be upon him, “The son of Adam fills no vessel worse than his stomach,” a legally defined evil, or is it evil in the customary sense? This is a matter requiring pause and reflection. There is no doubt that what is best and most excellent is what the Prophet, peace and blessings be upon him, instructed; put it into practice and you will see.

It has been said that among the destructive practices is eating more food before the food already in the stomach has been digested. If this is true, then it too is forbidden, for Allah says: “And do not kill yourselves. Surely Allah is ever merciful to you” [al-Nisa 4:29].

It is not far-fetched that this is correct, for it has been tested. They illustrate it with the example of a man who assigns workers a task to complete, then, before they have finished it, gives them another task. It is well known that they cannot work on both tasks except at the expense of one of them. If they begin the new task, the old one will be disrupted. Likewise, when the stomach receives new food, its digestion of the first food is disrupted—especially since Allah has made for digestion glands that secrete substances according to the length of time the food remains in the stomach.

According to physicians, digestion has stages: the first, second, third, and fourth stages of maturation. Therefore, there must be a proper balance, so that a person knows the stage—or degree—of the first food: can he add other food to it, or not?