(93) باب الصَّلاَةِ إِلَى الْعَنَزَةِ
Narrated Anas Ibn Malik:
Whenever the Prophet (ﷺ) went for answering the call of nature, I and another boy used to go after him with a staff, a stick or a short spear (or stick) and a tumbler of water and when he finished from answering the call of nature we would hand that tumbler of water to him.
Reference: Sahih al-Bukhari 500
In-book reference: Book 8, Hadith 147
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 9, Hadith 479