سنن النسائي

It was narrated from Ibn 'Umar that: When the Messenger of Allah (ﷺ) started to pray, he raised his hands until they were in level with his shoulders, and when he said the takbir before bowing, and when he raised his head from bowing he raised (his hands) likewise, and said: "Sami Allahu liman hamidah Rabbana wa lakal-hamd (Allah hears the one who praises Him; Our Lord, and to You be praise)," and he did not do that when prostrating.