(a) It is narrated from Abdullah bin Umar (may Allah be pleased with them both) that when the Messenger of Allah (peace and blessings be upon him) began the prayer, he raised both his hands up to his shoulders, and when he raised his head from the bowing he raised both hands in the same way, and he said 'Sami' Allahu liman hamidah' (Allah hears the one who praises Him), 'Rabbana wa lakal-hamd' (Our Lord, and to You belongs all praise). He (peace and blessings be upon him) did not do this in the prostrations (that is, he did not raise his hands).
(b) This narration is also reported from Malik, and in it there is the addition: and when he said the takbir for the bowing (he also raised his hands).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2501