Musnad Ahmad 25:1407

Sufyan narrated to us, from Ayyub, from Sa’id ibn Jubayr, from Ibn Abbas, who said: I came to him at Arafah, and I found him eating a pomegranate. He said: "Draw near and eat. Perhaps you are fasting?" "Indeed, the Messenger of Allah (peace and blessings of Allah be upon him) used not to fast it." And he said once: "Indeed, the Messenger of Allah (peace and blessings of Allah be upon him) did not fast this day."