Awn (may Allah have mercy on him) narrates from Sayyiduna Abdullah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When one of you bows, let him say 'Subhana rabbiya al-'azim' (Glory be to my Lord the Magnificent) three times; his bowing will be complete, and that is the minimum. Then when he prostrates, let him say 'Subhana rabbiya al-a'la' (Glory be to my Lord the Most High) three times; his prostration will be complete, and that is the minimum."
This is mursal; Awn bin Abdullah did not meet Abdullah bin Mas'ud (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2558