It was narrated from Hudhaifah bin Al-Yaman that he heard the Messenger of Allah (ﷺ) say when he bowed:“Subhana Rabbiyal-‘Azim (Glory is to my Lord, the Most Great)” three times, and when he prostrated he said: “Subhana Rabbiyal-A’la (Glory is to my Lord the Most High)” three times.
حَدَّثَنَا مُحَمَّدُ بْنُ رُمْحٍ الْمِصْرِيُّ، أَنْبَأَنَا ابْنُ لَهِيعَةَ، عَنْ عُبَيْدِ اللَّهِ بْنِ أَبِي جَعْفَرٍ، عَنْ أَبِي الأَزْهَرِ، عَنْ حُذَيْفَةَ بْنِ الْيَمَانِ، أَنَّهُ سَمِعَ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ يَقُولُ إِذَا رَكَعَ: " سُبْحَانَ رَبِّيَ الْعَظِيمِ " ثَلاَثَ مَرَّاتٍ، وَإِذَا سَجَدَ قَالَ: " سُبْحَانَ رَبِّيَ الأَعْلَى " ثَلاَثَ مَرَّاتٍ .
IbnMaja
Establishing the Prayer and the Sunnah Regarding Them • Hadith 888