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.
Sunan Abi Dawud Book 2, Hadith 611