Hadith 8:1494
Abu Bakr narrated to us, he said: Ya'la ibn 'Ubayd narrated to us, from 'Abd al-Malik, from 'Ata', who said: Arafat was only named [as such] because Gabriel used to show Abraham the rites, and he would say, "I have recognized [Araftu]." Then he would show him [more], and he would say, "I have recognized [Araftu]," so it was named Arafat.
حدثنا أبو بكر قال حدثنا يعلى بن عبيد عن عبد الملك عن عطاء قال إنما سميت عرفات لأن جبريل كان يري إبراهيم المناسك فيقول عرفت ثم يريه فيقول عرفت فسميت عرفات