Musnad Abu Ya'la al-Mawsili 110:25

Khalaf narrated to us, Abu al-Ahwas narrated to us, from Simak, from Ikrimah, from Ibn Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) ate a shoulder [of meat], then wiped his hand on a cloth that was beneath him, then stood up and prayed.