Musannaf Ibn Abi Shaybah

Hazrat Abu Majliz narrates that Hazrat Jibreel came to Ibrahim at Arafat and said, "Have you come to know?" He replied, "Yes." Because of this, it was named Arafat.

Hazrat Ata says that this place was named Arafat because Hazrat Jibreel used to teach Hazrat Ibrahim the rituals of Hajj and then ask, "Have you understood?" Then he would teach again and say, "Have you come to know?" For this reason, it was named Arafat.