كُنْتُ رَجُلاً مَذَّاءً فَأَمَرْتُ الْمِقْدَادَ أَنْ يَسْأَلَ النَّبِيَّ صلى الله عليه وسلم فَسَأَلَهُ فَقَالَ " فِيهِ الْوُضُوءُ ".
Ali ibn Abi Talib reported: I was a man who frequently had pre-seminal fluid (madhy), so I asked al-Miqdad to ask the Prophet ﷺ (about it). He asked him, and he said, “For it, ablution (wudu) is required.”
also in Sahih al-Bukhari 178, Sahih al-Bukhari 269