Whenever Ibn ʿUmar started the prayer with Takbir, he used to raise his hands: whenever he bowed, he used to raise his hands (before bowing) and also used to raise his hands on saying, "Samiʿa l-lahu liman hamidah", and he used to do the same on rising from the second rakʿa (for the 3rd rakʿa). Ibn ʿUmar said: "The Prophet ﷺ used to do the same."  

سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ رَفَعَ يَدَيْهِ وَإِذَا قَامَ مِنَ الرَّكْعَتَيْنِ رَفَعَ يَدَيْهِ وَرَفَعَ ذَلِكَ ابْنُ عُمَرَ إِلَى نَبِيِّ اللَّهِ ﷺ رَوَاهُ حَمَّادُ بْنُ سَلَمَةَ عَنْ أَيُّوبَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ عَنِ النَّبِيِّ ﷺ وَرَوَاهُ ابْنُ طَهْمَانَ عَنْ أَيُّوبَ وَمُوسَى بْنِ عُقْبَةَ مُخْتَصَرًا