When the Messenger of Allah ﷺ stood for prayer, he would raise his hands fully extended.
قال و حدثنا عبد الله بن عبد الرحمن أخبرنا عبيد الله بن عبد المجيد الحنفي حدثنا ابن أبي ذئب عن سعيد بن سمعان قال سمعت
كان رسول الله ﷺ إذا قام إلى الصلاة رفع يديه مدا
[Its chain is hasan] Abu Dawud also reported it, no. 753, from the hadith of Ibn Abu Dhib with the same chain, and Ibn Khuzayma graded it sahih, no. 473, as did Ibn Hibban (al-Ihsan): 1774, and Hakim, 1/134, and Dhahabi.