Sahih Bukhari
Bathing (Ghusl)
Volume: 001 / Book Number: 005 / Hadith Number: 269
Narrated 'Ali:
I used to get emotional urethral discharge frequently. Being the son-in-law of the Prophet I requested a man to ask him about it. So the man asked the Prophet about it. The Prophet replied, "Perform ablution after washing your organ (penis)."