Musannaf Ibn Abi Shayba 3:198

Abu Bakr narrated to us, he said: Waki’ and Abu Mu’awiyah narrated to us, from Ibn Abi Dhi’b, from Ishaq, from ‘Uwaymir, from ‘Awn ibn ‘Abd Allah, from Ibn Mas’ud, from the Prophet, may Allah bless him and grant him peace, who said: "When one of you bows, let him say 'Subhana Rabbi al-Azim' (Glory be to my Lord, the Magnificent) three times. And when he prostrates, let him say 'Subhana Rabbi al-A’la' (Glory be to my Lord, the Most High) three times. For if he does that, his bowing and his prostration have been completed, and that is the minimum of it."