It is narrated from Sayyiduna 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 his hands up to his shoulders, and when he raised his blessed head from bowing he raised his hands in the same way, and he said: 'Sami'allahu liman hamidah, rabbana wa lakal-hamd' (Allah has heard the one who praised Him; our Lord, and to You belongs all praise). But he (peace and blessings be upon him) did not do this (raising the hands) in the prostrations.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2604