It wasnarrated that Ibn Mas'ud said:
"The Messenger of Allah (ﷺ)said: 'When anyone of you bows, let him say in his bowing: "SubhanaRabbiyal-'Azim (Glory is to my Lord, the Most Great)" threetimes; ifhe does that his bowing will be complete. And when anyoneof youprostrates, let him say in his prostration, 'SubhanaRabbiyal-A'la(Glory if to my Lord, the Most High)" three times;if he does that,his prostration will be complete, and that is theminimum.'"
English reference: Vol. 1, Book 5, Hadith 890
Arabic reference: Book 5, Hadith 940