Musnad Ahmad 25:1605

'Abd al-Razzaq and Ibn Bakr narrated to us, they said: Ibn Jurayj informed us, he said: Muhammad ibn Yusuf informed me that Sulayman ibn Yasar informed him that he heard Ibn 'Abbas, and he saw Abu Hurayrah performing ablution. He [Abu Hurayrah] said: "Do you know what I am performing ablution from?" He said: "No." He said: "I am performing ablution from pieces of dried yogurt (aqt) that I ate." Ibn 'Abbas said: "I do not care what I perform ablution from. I bear witness that I saw the Messenger of Allah (peace and blessings of Allah be upon him) eat a shoulder of meat, then he stood up for prayer and did not perform ablution." Sulayman was present for that from both of them.