Sunan an-Nasai Book 13, Hadith 1182

أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى الصَّنْعَانِيُّ، قَالَ حَدَّثَنَا الْمُعْتَمِرُ، قَالَ سَمِعْتُ عُبَيْدَ اللَّهِ، - وَهُوَ ابْنُ عُمَرَ - عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمٍ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُ كَانَ يَرْفَعُ يَدَيْهِ إِذَا دَخَلَ فِي الصَّلاَةِ وَإِذَا أَرَادَ أَنْ يَرْكَعَ وَإِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ وَإِذَا قَامَ مِنَ الرَّكْعَتَيْنِ يَرْفَعُ يَدَيْهِ كَذَلِكَ حَذْوَ الْمَنْكِبَيْنِ ‏.‏

It was narrated from Ibn 'Umar that :The Prophet (ﷺ) used to raise his hands when he began to pray, when he wanted to bow, when he raised his head from bowing, and when he stood up after the first two rak'ahs, he would raise his hands likewise, level with his shoulders