Sunan an-Nasai Book 11, Hadith 878

أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا افْتَتَحَ الصَّلاَةَ رَفَعَ يَدَيْهِ حَذْوَ مَنْكِبَيْهِ وَإِذَا رَكَعَ وَإِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ رَفَعَهُمَا كَذَلِكَ وَقَالَ ‏ "‏ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ رَبَّنَا وَلَكَ الْحَمْدُ ‏"‏ ‏.‏ وَكَانَ لاَ يَفْعَلُ ذَلِكَ فِي السُّجُودِ ‏.‏

It was narrated from Abdullah bin Umar :that when the Messenger of Allah (ﷺ) started to pray, he would raise his hands in level with his shoulders, and when he bowed and when he raised his head from bowing, he would raise them likewise and say "Sami Allahu liman hamidah, Rabbana wa lakal-hamd (Allah hears those who praise Him, our Lord, to You be praise." And he did not do that when he prostrated)