Sunan Ibn Majah — Establishing the Prayer and the Sunnah Regarding Them — Hadith No: 890
Translation
It was narrated that Ibn Mas’ud said:“The Messenger of Allah (ﷺ) said: ‘When anyone of you bows, let him say in his bowing: “Subhana Rabbiyal-‘Azim (Glory is to my Lord, the Most Great)” three times; if he does that his bowing will be complete. And when anyone of you prostrates, let him say in his prostration, ‘Subhana Rabbiyal-A’la (Glory if to my Lord, the Most High)” three times; if he does that, his prostration will be complete, and that is the minimum.’”