Sunan an Nasai
157
Sahih+2

It was narrated that 'Ali said:"I felt too shy to ask the Messenger of Allah (ﷺ) about prostatic fluid because of Fatimah, so I told Al-Miqdad bin Al-Aswad to ask about it, and he (the Prophet (ﷺ)) said: 'Perform Wudu' for that

SahihAbu Ghuddah
SahihAl-Albani