Abu Dawud Book 1, Hadith Number 206.
Chapter : On prostatic fluid madhi.
Narated By ‘Ali : My prostatic fluid flowed excessively. I used to take a bath until my back cracked (because of frequent washing). I mentioned it to the Prophet (may peace be upon him), or the fact was mentioned to him (by someone else). The Apostle of Allah (may peace be upon him) said: Do not do so. When you find pro-static fluid, wash your penis and perform ablution as you do for prayer, but when you have seminal emission, you should take a bath.”