Sunan Ibn Majah, Volume 2, Book 5, Hadith 866 (DarusSalam) ⓘ
It was narrated from Anas that the Messenger of Allah used to raise his hands when he entered prayer, and when he bowed in Ruku’.”
حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا عَبْدُ الْوَهَّابِ، حَدَّثَنَا حُمَيْدٌ، عَنْ أَنَسٍ، أَنَّ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ كَانَ يَرْفَعُ يَدَيْهِ إِذَا دَخَلَ فِي الصَّلاَةِ وَإِذَا رَكَعَ .
also referenced under: Hadith 866 (Reference) & Book 5, Hadith 915 (In-Book)