The Messenger of Allah ﷺ entered upon us while the people were raising their hands. The narrator Zubair said: I think( they were raising the hands) during prayer. He (the prophet) said: What is the matter, I see you raising your hands as if they are the tails of restive horses! Maintain tranquility during prayer. (Using translation from Abū Dāʾūd 1000)
دَخَلَ عَلَيْنَا رَسُولُ اللهِ ﷺ الْمَسْجِدَ فَرَآهُمْ رَافِعِي أَيْدِيهِمْ فِي الصَّلَاةِ فَقَالَ «مَا لِي أَرَاهُمْ رَافِعِي أَيْدِيهِمْ كَأَنَّهَا أَذْنَابُ الْخَيْلِ الشُّمُسِ؟ اسْكُنُوا فِي الصَّلَاةِ»