Sunan an-Nasai Book 12, Hadith 1059

أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا افْتَتَحَ الصَّلاَةَ رَفَعَ يَدَيْهِ حَذْوَ مَنْكِبَيْهِ وَإِذَا كَبَّرَ لِلرُّكُوعِ وَإِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ رَفَعَهُمَا كَذَلِكَ أَيْضًا وَقَالَ ‏ "‏ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ رَبَّنَا وَلَكَ الْحَمْدُ ‏"‏ ‏.‏ وَكَانَ لاَ يَفْعَلُ ذَلِكَ فِي السُّجُودِ ‏.‏

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