Sahih Bukhari Volume 1, Book 10, Hadith 796

حَدَّثَنَا آدَمُ، قَالَ حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ، عَنْ سَعِيدٍ الْمَقْبُرِيِّ، عَنْ أَبِي هُرَيْرَةَ، قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم إِذَا قَالَ ‏"‏ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ ‏"‏‏.‏ قَالَ ‏"‏ اللَّهُمَّ رَبَّنَا وَلَكَ الْحَمْدُ ‏"‏‏.‏ وَكَانَ النَّبِيُّ صلى الله عليه وسلم إِذَا رَكَعَ وَإِذَا رَفَعَ رَأْسَهُ يُكَبِّرُ، وَإِذَا قَامَ مِنَ السَّجْدَتَيْنِ قَالَ ‏"‏ اللَّهُ أَكْبَرُ ‏"

Narrated By Abu Huraira : When the Prophet said, "Sami' a-l-lahu Liman hamida," (Allah heard those who sent praises to Him), he would say, "Rabbana wa-laka-l-hamd." On bowing and raising his head from it the Prophet used to say Takbir. He also used to say Takbir on rising after the two prostrations.