It was narrated that Ibn Mas' ud said: "The Messenger of Allah P.B.U.H 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-Ala (Glory is to my Lord, the Most High)" three times; if he does that, his prostration will be complete, and that is the minimum. ", (Da'if)