Musannaf Ibn Abi Shayba 3:730

Zayd ibn al-Hubab narrated to us, he said: Mu'awiyah ibn Salih informed me, he said: Malik ibn Ziyad al-Ashja'i narrated to me, he said: I heard Umar ibn Abd al-Aziz saying: "It is from the completion of the prayer that you say when you finish: 'There is no god but Allah, alone, He has no partner; to Him belongs the dominion, and to Him belongs the praise, and He is capable of all things,' three times."