The Book of Purification
1/112. Chapter:
What Invalidates Wudu' And What Does Not Invalidate Wudu' Of Madhi (Prostatic Fluid)
Sunan an-Nasai
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَخْبَرَنَا جَرِيرٌ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ عَلِيٍّ، - رضى الله عنه - قَالَ قُلْتُ لِلْمِقْدَادِ إِذَا بَنَى الرَّجُلُ بِأَهْلِهِ فَأَمْذَى وَلَمْ يُجَامِعْ فَسَلِ النَّبِيَّ صلى الله عليه وسلم عَنْ ذَلِكَ فَإِنِّي أَسْتَحِي أَنْ أَسْأَلَهُ عَنْ ذَلِكَ وَابْنَتُهُ تَحْتِي . فَسَأَلَهُ فَقَالَ " يَغْسِلُ مَذَاكِيرَهُ وَيَتَوَضَّأُ وُضُوءَهُ لِلصَّلاَةِ " .
It was narrated that 'Ali said: "I said to Al-Miqdad: 'If a man is intimate with his wife and excretes prostatic fluid but does not have intercourse - ask the Prophet (ﷺ) about that, for I am too shy to ask him about it since his daughter is married to me.' So he asked him, and he said: 'Let him wash his male member and perform Wudu' as for Salah.'"
Reference : Sunan an-Nasa'i 153In-book reference : Book 1, Hadith 154English translation : Vol. 1, Book 1, Hadith 153