Musnad Ahmad 30:2723

Hajjaj narrated to us, he said: Layth narrated to us, he said: Aqil ibn Khalid narrated to me, from Ibn Shihab, that he said: Abu Bakr ibn Abd al-Rahman ibn al-Harith informed me that he heard Abu Hurayrah saying: When the Messenger of Allah (peace and blessings of Allah be upon him) stood for prayer, he would say the takbir (Allahu Akbar) when he stood. Then he would say the takbir when he bowed. Then he would say: "Sami' Allahu liman hamidah" (Allah hears those who praise Him) when he raised his back from the bowing position. Then he would say while standing: "Rabbana wa lakal-hamd" (Our Lord, and to You is the praise). Then he would say the takbir when he descended to prostrate. Then he would say the takbir when he raised his head. Then he would say the takbir when he descended to prostrate. Then he would say the takbir when he raised his head. Then he would do that throughout the entire prayer until he finished it, and he would say the takbir when he stood up from the two [rak'ahs] after the sitting.