Sahih Muslim, Chapter: Prayers (Kitab Al-Salat)

that the Messenger of Allah (may peace be upon him), when he stood up for prayer, used to raise his hands apposite the shoulders and then recited takbir (Allah-’o-’Akbar), and when he was about to bow he again did like it and when he raised himself from the ruku' (bowing posture) he again did like it, but he did not do it at the time of raising his head from prostration.