When he began the prayer, he would say the takbir and raise his hands. When he bowed, he raised his hands. When he said, "Allah hears whoever praises Him," he raised his hands. And when he stood up after the first two rakats, he raised his hands. Ibn Umar traced this back to the Prophet of Allah ﷺ.Hammad bin Salama narrated it from Ayub, from Nafi, from Ibn Umar, from the Prophet ﷺ. Ibn Tahman also narrated it from Ayub and Musa bin Uqba in an abridged form.
حدثنا عياش قال حدثنا عبد الأعلى قال حدثنا عبيد الله عن نافع أن
كان إذا دخل في الصلاة كبر ورفع يديه وإذا ركع رفع يديه وإذا قال سمع الله لمن حمده رفع يديه وإذا قام من الركعتين رفع يديه ورفع ذلك ابن عمر إلى نبي الله ﷺ رواه حماد بن سلمة عن أيوب عن نافع عن ابن عمر عن النبي ﷺ ورواه ابن طهمان عن أيوب وموسى بن عقبة مختصرا