It is narrated from Sayyiduna Ibn 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 also when he bowed or rose from the bowing (he raised both hands at all of these points).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2510