"Alqamah bin Wa'il told us that his father said: "I saw the Messenger of Allah ﷺ, when he was standing in prayer, holding his left hand with his right.'" (Using translation from Nasāʾī 887)
«رَأَيْتُ رَسُولَ اللهِ ﷺ إِذَا كَانَ قَائِمًا فِي الصَّلَاةِ قَبَضَ بِيَمِينِهِ عَلَى شِمَالِهِ»