The Messenger of Allah ﷺ came out to us while we were raising our hands in the prayer, and he said, "What is the matter with them, raising their hands in the prayer as though they were the tails of restive horses? Be still in the prayer."
أخبرنا قتيبة بن سعيد قال حدثنا عبثر عن الأعمش عن المسيب بن رافع عن تميم بن طرفة
خرج علينا رسول الله ﷺ ونحن رافعو أيدينا في الصلاة فقال ما بالهم رافعين أيديهم في الصلاة كأنها أذناب الخيل الشمس اسكنوا في الصلاة
No references are available.
Muslim reported it in the Book of Prayer, chapter on the command to remain still in prayer, etc., hadith 430, from the hadith of Amash with this same chain, and it is also found in Kubra, hadith 1107.