Musnad Abu Ya'la al-Mawsili 1:75

Ubayd Allah ibn Umar narrated to us, Abd al-Rahman ibn Mahdi narrated to us, Hushaym narrated to us, from Ya'la ibn 'Ata, from Amr ibn 'Asim, from Abu Hurayrah, that Abu Bakr said: "O Messenger of Allah, teach me words that I may say when I reach the morning and when I reach the evening." He said: "Say: 'O Allah, Creator of the heavens and the earth, Knower of the unseen and the witnessed, You are the Lord of everything and its Sovereign. There is no god but You. I seek refuge in You from the evil of my soul, and from the evil of Satan and his shirk (polytheism/entrapment).'" "Say it when you reach the morning, when you reach the evening, and when you go to your bed."