"I saw the Messenger of Allah ﷺ, when he stood to pray, raise his hands until they were in level with his shoulders, then he said the takbir. He did that when he said the Takbir before bowing, and he did that when he raised his head from bowing and said: 'Sami Allahu liman hamidah (Allah hears those who praise Him).' Bu he did not do that during the prostration." (Using translation from Nasāʾī 877)  

رَأَيْتُ رَسُولَ اللهِ ﷺ إِذَا قَامَ إِلَى الصَّلَاةِ رَفَعَ يَدَيْهِ حَتَّى تَكُونَا حَذْوَ مَنْكِبَيْهِ ثُمَّ يُكَبِّرُ قَالَ وَكَانَ يَفْعَلُ ذَلِكَ حِينَ يُكَبِّرُ لِلرُّكُوعِ وَيَفْعَلُ ذَلِكَ حِينَ يَرْفَعُ رَأْسَهُ مِنَ الرُّكُوعِ فَيَقُولُ «سَمِعَ اللهُ لِمَنْ حَمِدَهُ» وَلَا يَفْعَلُ ذَلِكَ فِي السُّجُودِ