Muhammad bin Amr bin Ata (may Allah have mercy on him) said: I heard Sayyiduna Abu Humayd al-Sa'idi (may Allah be pleased with him), while sitting among ten Companions of the Messenger of Allah (peace and blessings be upon him), among whom was Sayyiduna Abu Qatadah al-Harith bin Rib'i (may Allah be pleased with him), say: "I know more than all of you about the prayer of the Messenger of Allah (peace and blessings be upon him)." It also contains that he (peace and blessings be upon him) would raise both his hands level with his shoulders when he began the prayer, when he bowed, and when he rose from bowing. Then, when he stood up after two rak'ahs, he would say the takbir and raise both hands to his shoulders, just as he raised them with the takbir at the beginning of the prayer. Then he would do the same in the rest of his prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2816