Musannaf Ibn Abi Shayba 1:540

Ghundar and Waki’ narrated to us, from Shu’bah, from Muhammad ibn ‘Abd al-Rahman ibn Zurarah, that he heard Muhammad ibn ‘Amr ibn Abi [al-Hasan] narrating from Umm al-Tufayl, the wife of Ubayy, that Ubayy used to eat tharid. Then he would rinse his mouth and pray.