What is the evidence for specifying the distance for shortening prayers (qasr) as 83 kilometers, and what is the answer regarding the Prophet's (peace be upon him) shortening of prayers in Arafah, which is 18 kilometers from Mecca?

Some scholars hold the view that shortening prayers in Mecca for pilgrims is not due to travel, but rather due to the rites of Hajj. Others believe that shortening prayers does not require a specific distance, but rather is determined by custom. They cite the actions of the Prophet, peace and blessings be upon him, and his successors, who shortened prayers at Arafat, Muzdalifah, and Mina, and did not order the people of Mecca to pray in full. This indicates that the travel for which prayers are shortened is not limited by a known distance or time.