I used to serve the Messenger of Allah ﷺ. Whenever he wanted to bathe, he would say, "Turn your back toward me." So I would turn my back toward him and screen him with it.
أخبرنا مجاهد بن موسى قال حدثنا عبد الرحمن بن مهدي قال حدثني يحيى بن الوليد قال حدثني محل بن خليفة قال حدثني
كنت أخدم رسول الله ﷺ فكان إذا أراد أن يغتسل قال ولني قفاك فأوليه قفاي فأستره به
[Its chain of transmission is sahih] Abu Dawud reported it in Taharah, chapter on the urine of the infant that gets on clothing, hadith 376, and Ibn Majah in Taharah, chapter on what has been said about the urine of the infant who has not yet eaten food, hadith 526, from Mujahid through this route, and it is also in the Kubra, hadith 228. Ibn Khuzayma and Hakim (1/166) graded it sahih, as did Dhahabi, while Bukhari graded it hasan (Talkhis Habir, 1/38).