‘Ali said: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 Messenger of Allah (May peace be upon him) said; Do not do so. When you find prostatic fluid, wash your penis and perform ablution as you do for your prayer, but when you have seminal emission, you should take a bath.
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا عَبِيدَةُ بْنُ حُمَيْدٍ الْحَذَّاءُ، عَنِ الرُّكَيْنِ بْنِ الرَّبِيعِ، عَنْ حُصَيْنِ بْنِ قَبِيصَةَ، عَنْ عَلِيٍّ، - رضى الله عنه - قَالَ كُنْتُ رَجُلاً مَذَّاءً فَجَعَلْتُ أَغْتَسِلُ حَتَّى تَشَقَّقَ ظَهْرِي فَذَكَرْتُ ذَلِكَ لِلنَّبِيِّ صلى الله عليه وسلم - أَوْ ذُكِرَ لَهُ - فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ تَفْعَلْ إِذَا رَأَيْتَ الْمَذْىَ فَاغْسِلْ ذَكَرَكَ وَتَوَضَّأْ وُضُوءَكَ لِلصَّلاَةِ فَإِذَا فَضَخْتَ الْمَاءَ فَاغْتَسِلْ " .
AbuDaud
Purification (Kitab Al-Taharah) • Hadith 206