Sahih al-Bukhari 735
Narrated Salim bin `Abdullah:
My father said, "Allah's Messenger (ﷺ) used to raise both his hands up to the level of his shoulders when 
opening the prayer; and on saying the Takbir for bowing. And on raising his head from bowing he 
used to do the same and then say "Sami`a l-lahu liman hamidah, Rabbana wa laka l-hamd." And he 
did not do that (i.e. raising his hands) in prostrations.
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَرْفَعُ يَدَيْهِ حَذْوَ مَنْكِبَيْهِ إِذَا افْتَتَحَ الصَّلاَةَ، 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.‏