We were with the Prophet ﷺ when he nudged my back, or my shoulder, with something he had with him. I followed him, and the Messenger of Allah ﷺ relieved himself, then came back and asked, "Do you have water with you?"I replied, "Yes, I have a small water-skin with me."He washed his face. He was wearing a Syrian outer garment with narrow sleeves, so he slipped his hand inside and lifted the garment up onto his shoulder, drawing his arms out from beneath it. He washed his forearms, wiped over his turban, and mentioned something about wiping the front of his head, and wiped over his leather socks.Then we set out and caught up with the people in the morning prayer, with Abdul-Rahman leading them. They had already prayed one rakah. I went to inform him, but the Prophet ﷺ forbade me. So we prayed one rakah with him, and afterwards made up the rakah we had missed.
حدثنا يزيد بن هارون أخبرنا ابن عون عن الشعبي
كنا مع النبي ﷺ فغمز ظهري أو كتفي بشيء كان معه قال وتبعته فقضى رسول الله ﷺ حاجته ثم جاء فقال أمعك ماء قلت نعم ومعي سطيحة من ماء فغسل وجهه وكانت عليه جبة شامية ضيقة الكمين فأدخل يده فرفع الجبة على عاتقه وأخرج يديه من أسفل الجبة فغسل ذراعيه ومسح على العمامة قال وذكر الناصية بشيء ومسح على خفيه ثم أقبلنا فأدركنا القوم في صلاة الغداة وعبد الرحمن يؤمهم وقد صلوا ركعة فذهبت لأوذنه فنهاني فصلينا معه ركعة وقضينا التي سبقنا بها
Its isnad is sahih. Urwa bin Mughira is a trustworthy tabii, and the hadith has already appeared at 18052.