Sahih Bukhari

Narated By 'Abdullah bin 'Umar : I saw Allah's Apostle opening the prayer with the Takbir and raising his hands to the level of his shoulders at the time of saying the Takbir, and on saying the Takbir for bowing he did the same; and when he said, "Sami a-l-lahu Liman hamida ", he did the same and then said, "Rabbana wa laka-l-hamd." But he did not do the same on prostrating and on lifting the head from it."