Whenever the Messenger of Allah ﷺ went to relieve himself, I and another boy of about my age would carry a small water vessel for him, and he would clean himself with the water.
أخبرنا إسحق بن إبراهيم قال أنبأنا النضر قال أنبأنا شعبة عن عطاء بن أبي ميمونة قال سمعت
كان رسول الله ﷺ إذا دخل الخلاء أحمل أنا وغلام معي نحوي إداوة من ماء فيستنجي بالماء
Agreed upon, and Bukhari included it in the Book of Wudu, the chapter on cleansing with water, and in the Book of Purification, the chapter on cleansing with water after relieving oneself, hadith (271), from the hadith of Shubah with this wording. It is also found in Al-Kubra, hadith (47).