Mishkat al-Masabih 302
‘Ali said:
My prostatic fluid flowed readily, and I was ashamed to consult the Prophet because of the position of his daughter so I gave orders to al-Miqdad to consult him, and the Prophet said, “He must wash his penis and perform ablution.” 

(Bukhari and Muslim.)
وَعَن عَليّ قَالَ: كُنْتُ رَجُلًا مَذَّاءً فَكُنْتُ أَسْتَحْيِي أَنْ أَسْأَلَ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لِمَكَانِ ابْنَتِهِ فَأَمَرْتُ الْمِقْدَادَ فَسَأَلَهُ فَقَالَ: «يَغْسِلُ ذَكَرَهُ وَيتَوَضَّأ»