It is narrated from Hazrat Wa'il (may Allah be pleased with him) that he saw the Prophet Muhammad (peace and blessings be upon him) raising his hands with the takbeer, and during the prayer, he saw him placing his right hand over his left hand.
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 18852