What is the evidence for defining the distance of travel as eighty kilometers?

Question:
He says: Honorable Shaykh, may Allah grant you success, is there evidence for defining the distance of travel as eighty kilometers? And how did they arrive at this limit?

Answer:
Yes, because the Messenger (peace and blessings be upon him) said a two-day journey, a two-day journey, except for Mu'adh and the one in ihram. The two days are two stages for the mount, each stage being forty kilometers. The stage one walks on foot in a day is forty kilometers; he cannot increase beyond that, and the mount cannot travel more than forty in a day. This is the custom and what is known among the Arabs, so they took from this hadith the estimation of the distance in travel. Yes. We say: Honorable Shaykh, may Allah grant you success. This indicates that what is less than this is not called travel that requires a mahram for a woman. Yes.