Saeed bin Jubair narrates: I came to Abdullah bin Abbas (may Allah be pleased with them both) at Arafah, and I saw him eating pomegranate. He said: Come forward and eat as well! Perhaps you are fasting; the Prophet Muhammad (peace be upon him) did not fast on this day.
Shaykh Muhammad Ibrahim bin Basheer
Benefit: In this hadith, it is stated that on the Day of Arafah, the pilgrims who are present in the plain of Arafah will not fast; apart from them, the rest of the Muslim Ummah will fast on the Day of Arafah, the 9th of Dhul-Hijjah. The great virtue of this fast has been reported. It is narrated from Sayyiduna Abu Qatadah Al-Ansari radi Allahu anhu that the Messenger of Allah sallallahu alayhi wa sallam was asked about fasting on the Day of Arafah, so he sallallahu alayhi wa sallam said: "It expiates the sins of the previous year and the coming year." [صحيح مسلم : 1162]
Source: Musnad al-Humaydi: Commentary by Muhammad Ibrahim bin Bashir, Page: 522