Ibn Shihab (may Allah have mercy on him) said: Abu Bakr bin Abd al-Rahman informed me that he heard Sayyiduna Abu Hurayrah (may Allah be pleased with him) say: When the Messenger of Allah (peace and blessings be upon him) stood for prayer, he said the takbir, then he said the takbir when bowing, then he said 'Sami'allahu liman hamidah' (Allah has heard the one who praised Him), and when he had straightened his back from bowing he said 'Rabbana wa lakal-hamd' (Our Lord, and to You belongs all praise). Then he mentioned the complete hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2603