Musannaf Ibn Abi Shayba 1:564

Ghundar narrated to us, from Shu'bah, who said: I heard Abu Ishaq narrating that he heard Abu al-Safar narrating from Abdullah ibn Amr, who said: They were with al-Mughirah ibn Shu'bah, and they ate meat and tharid. They went out from his presence and began to pray without performing ablution. Abu Mas'ud said: "Look, they are praying and not performing ablution."