omitted noun; the intended meaning is: “a vigorous running.” Here, sa‘i means running. Thus, he should run vigorously as much as he is able, provided that he neither harms himself nor harms others. If he fears harm to himself or to someone else, then he should walk and perform sa‘i as much as is manageable. Likewise, if women are with him and he fears for their safety, the requirement of running vigorously is waived for him.
The evidence for this is the action of the Messenger of Allah, peace and blessings be upon him: he would run until his lower garment whirled about him from the intensity of his running. (1)
If someone were to ask: What is the wisdom behind running vigorously between the two markers?
The answer is that this place used to be a valley—that is, a channel for rainwater. A valley is generally sloping and has soft, sandy ground, making ordinary walking difficult; so one runs.
The underlying purpose of sa‘i is for a person to recall the state of Ishmael’s mother, Hagar—may Allah be pleased with her. When Abraham, peace be upon him, left her and her son in this place, he left with her a waterskin of water and a bag of dates. The mother would eat from the dates, drink from the water, and nurse her child. Then the water ran out, as did the dates; she grew hungry and thirsty, and her breasts dried up,