Sunan Ibn Majah Book 5, Hadith 86
“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.
“When the following was revealed: ‘So glorify the Name of your Lord, the Most Great’, the Messenger of Allah (ﷺ) said to us: ‘Say this in your Ruku’.’ And when the following was revealed: ‘Glorify the Name of your Lord, the Most High.’ the Messenger of Allah (ﷺ) said to us: ‘Say this in your prostrations.’”
“The Messenger of Allah (ﷺ) often used to say when bowing and prostrating: ‘Subhanak Allahumma wa bi hamdika, Allahummaghfir li (Glory be to You, O Allah, and praise; O Allah forgive me),’ following the command given by the Qur’an.”[Surat An-Nasr (110)]