Sunan an-Nasa'i 152

أَخْبَرَنَا هَنَّادُ بْنُ السَّرِيِّ، عَنْ أَبِي بَكْرِ بْنِ عَيَّاشٍ، عَنْ أَبِي حَصِينٍ، عَنْ أَبِي عَبْدِ الرَّحْمَنِ، قَالَ قَالَ عَلِيٌّ كُنْتُ رَجُلاً مَذَّاءً وَكَانَتِ ابْنَةُ النَّبِيِّ صلى الله عليه وسلم تَحْتِي فَاسْتَحْيَيْتُ أَنْ أَسْأَلَهُ فَقُلْتُ لِرَجُلٍ جَالِسٍ إِلَى جَنْبِي سَلْهُ ‏.‏ فَسَأَلَهُ فَقَالَ ‏ "‏ فِيهِ الْوُضُوءُ ‏"‏ ‏.‏

Ali said:"I was a man who had a lot of prostatic discharge, and the daughter of the Prophet (ﷺ) was married to me, so I felt shy to ask him (about that). I said to a man who was sitting beside me: 'Ask him,' so he asked him and he said: 'Perform Wudu' for that

Reference

Sunan an-Nasa'i 152

In-book

Book 1, Hadith 153