Musnad Ahmad 650:9

'Abdullah narrated to us, my father narrated to me, he said: I heard Yahya bin Sa'id saying: "Mutarrif is twenty years older than al-Hasan, and Abu al-'Ala' is ten years older than al-Hasan." 'Abdullah said: My father said: "A brother of Abu Bakr bin Abi al-Aswad narrated it to me, from Yahya bin Sa'id, from Abu 'Aqil al-Dawraqi, with this."