Practising Rafa’ yadain (literally means raising of two hands) during salaah is a sunnah reported in many ahaadiths.
My father said, “Allāh’s Apostle 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
Similar hadīth has also been narrated `Ali ibn Abi Talib. He said,
When the Messenger of Allāh stood for offering the obligatory prayer,
When he stood up from his prostrations (at the end of two rak’ahs), he raised his hands likewise and uttered the takbir and raised his hands so as to bring them up to his shoulders, as he uttered the takbir at the beginning of the prayer. – Abu Dawood