The Prophet ﷺ urinated, then sprinkled water on his private area.
حدثنا سفيان عن ابن أبي نجيح عن مجاهد
أن النبي ﷺ بال فنضح فرجه
No references are available.
Its isnad is daif, due to the anonymity of the narrator from the companion. As for Ibn Abu Najeeh, he is Abdullah, and he is a well-known trustworthy narrator. The hadith is sahih, and it has appeared previously at 15322.