Musnad Ahmad 5:150

Abu Ahmad al-Zubayri narrated to us, Ali bin Salih narrated to us, from Abu Ishaq, from Amr bin Murrah, from Abdullah bin Salamah, from Ali, who said: The Prophet, may Allah bless him and grant him peace, said to me: "Shall I not teach you words that, if you say them, you will be forgiven—even though you are already forgiven: There is no god but Allah, the Forbearing, the Generous. There is no god but Allah, the Most High, the Magnificent. Glory be to Allah, Lord of the seven heavens and Lord of the Magnificent Throne. Praise be to Allah, Lord of the worlds."