Musannaf Ibn Abi Shayba 17:1221

Ghundar narrated to us, from Shu'bah, from Ya'la ibn 'Ata, who said: I heard 'Amr ibn 'Asim narrating that he heard Abu Hurayrah, that Abu Bakr said to the Prophet, peace and blessings of Allah be upon him: "Inform me of something I should say when I reach the evening and when I reach the morning." He said: "Say: 'O Allah, Knower of the unseen and the witnessed, Creator of the heavens and the earth, Lord of everything and its Sovereign, I bear witness that there is no god but You. I seek refuge in You from the evil of my soul, and from the evil of the devil and his shirk (polytheism/entrapment).' Say it when you reach the evening and when you take to your bed."