Musnad Ahmad 1:62

'Affan narrated to us, he said: Shu'bah narrated to us, from Ya'la ibn 'Ata, he said: I heard 'Amr ibn 'Asim ibn 'Abdullah, he said: I heard Abu Hurairah saying: Abu Bakr said: "O Messenger of Allah, tell me something to say when I reach the morning and when I reach the evening." He said: "Say: 'O Allah, Knower of the unseen and the witnessed, Creator of the heavens and the earth, Lord of everything and its Possessor, 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/traps).'" And he commanded him to say it when he reached the morning, when he reached the evening, and when he took to his bed.