(30) باب الْوُضُوءِ مِنْ مَسِّ الذَّكَرِ
It was narrated that Marwan bin Al-Hakam said that one should perform Wudu' after touching one's penis. Marwan said:
"Busrah bint Safwan told me that." 'Urwah sent someone to check that, and she said: "The Messenger of Allah (ﷺ) mentioned what Wudu' is done for, and said: 'Touching the penis.'"
Reference: Sunan an-Nasa'i 446
In-book reference: Book 4, Hadith 52
English translation: Vol. 1, Book 4, Hadith 447