Musnad Ahmad 30:912

'Abd al-Rahman ibn Mahdi narrated to us, Hawshab ibn 'Aqil narrated to us, Mahdi al-Muharibi narrated to me, 'Ikrimah, the freed slave of Ibn 'Abbas, narrated to me, he said: I entered upon Abu Hurayrah in his house, and I asked him about fasting the day of 'Arafah at 'Arafat. He said: "The Messenger of Allah, peace and blessings of Allah be upon him, forbade fasting the day of 'Arafah at 'Arafat." And 'Abd al-Rahman said once: "From Mahdi al-'Abdi."