Volume 2 · Book 26 · Hadith 819
Narrated Ibn Abbas: Staying at Al-Mahassab is not one of the ceremonies (of Hajj), but Al-Mahassab is a place where Allah's Apostle camped (during his Hajjat-ul-wida).
— Sahih Bukhari, Volume 2, Book 26: Pilgrimmage (Hajj), Hadith #819