Sayyiduna Uqbah bin Amir (may Allah be pleased with him) said that when the Messenger of Allah (peace and blessings be upon him) bowed he would say 'Subhana rabbiya al-'azimi wa bihamdih' (Glory be to my Lord the Magnificent, and all praise is His) three times, and when he prostrated he would say 'Subhana rabbiya al-a'la wa bihamdih' (Glory be to my Lord the Most High, and all praise is His) three times.
Imam Abu Dawud (may Allah have mercy on him) said: We fear that this addition may not be preserved (mahfuz).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2556