Musannaf Ibn Abi Shayba 21:80

Ubaydah ibn Humayd narrated to us, from Mansur, from al-Sha'bi, who said: Umm Salamah said: When the Prophet (peace and blessings of Allah be upon him) would go out, he would say: "O Allah, I seek refuge in You from slipping or being caused to slip, or oppressing or being oppressed, or acting ignorantly or having ignorance acted upon me."