When the Prophet of Allah ﷺ started to pray, he raised his hands, and when he bowed, he did likewise, and when he raised his head from bowing he did likewise, and when he raised his head from prostration, he did likewise, meaning he raised his hands. (Using translation from Nasāʾī 1143)  

أَنَّ نَبِيَّ اللهِ ﷺ كَانَ «إِذَا دَخَلَ فِي الصَّلَاةِ وَإِذَا رَكَعَ فَعَلَ مِثْلَ ذَلِكَ وَإِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ فَعَلَ مِثْلَ ذَلِكَ وَإِذَا رَفَعَ رَأْسَهُ مِنَ السُّجُودِ فَعَلَ مِثْلَ ذَلِكَ كَأَنَّهُ يَعْنِي رَفَعَ يَدَيْهِ»