Sahih Bukhari
Ablutions (Wudu)
Volume: 001 / Book Number: 004 / Hadith Number: 178
Narrated 'Ali:
I used to get emotional urethral discharges frequently and felt shy to ask Allah's Apostle about it. So I requested Al-Miqdad bin Al-Aswad to ask (the Prophet ) about it. Al-Miqdad asked him and he replied, "On has to perform ablution (after it)."