been mentioned in his words, when he was sent to all mankind? The distance that constitutes travel must therefore be common knowledge. Measuring the land is not practicable; indeed, it is either impossible or exceedingly difficult. Even if kings and others like them can survey a road, they can only measure it along a straight line or along precisely defined curves. Yet travellers may know other routes and may take them, and the route may include uphill stretches. Some people’s journeys take longer because they move slowly, while others’ take less time because they move quickly. The operative cause is travel itself, not the measured extent of the land.

What we find in the words of the Prophet—may Allah bless him and grant him peace—and the Companions is the measurement of distances in terms of time, as in his statement about the Cistern:

“Its length is a month’s journey, and its breadth is a month’s journey.”

And his statement:

“Between heaven and earth are five hundred years.”

Another hadith states:

“Seventy-one, seventy-two, or seventy-three years.”

It has been said that the first refers to the usual pace of travel, on camelback or on foot, while the second refers to the pace of postal couriers, who ordinarily cover seven times the distance covered at the usual pace. Likewise, the Companions would speak of “a full day” or “two days.” Hence, those who set the limit at forty-eight miles described it as two days’ travel at a moderate pace, on camelback or on foot. But there is no evidence for this.

That being so, we say: whenever a term has no defined limit in either the language or the revealed law, customary usage is the point of reference. Thus, whatever counts as travel in people’s customary usage is