Sunan Ibn Majah
3010
Sahih+3

It was narrated that ‘Ali said:“The Messenger of Allah (ﷺ) stopped at ‘Arafat and said: ‘This is the place of standing, and all of ‘Arafat is a place of standing.’”

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi