Bulugh al-Maram, Book 1, Hadith 82 (In-Book)

Narrated ‘Ali bin Abi Talib (rad): I was one who Madhi (urethral discharge) flowed readily and asked Miqdad (his slave) to ask the Prophet about it. He (the Prophet) said:“One should perform Wudu (ablution) in this case”. [Agreed upon and this is Al-Bukhari’s version].

وَعَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ ‏- رضى الله عنه ‏- قَالَ: { كُنْتُ رَجُلاً مَذَّاءً, فَأَمَرْتُ اَلْمِقْدَادَ بْنَ اَلْأَسْوَدِ أَنْ يَسْأَلَ اَلنَّبِيَّ ‏- صلى الله عليه وسلم ‏-فَسَأَلَهُ ? فَقَالَ: "فِيهِ اَلْوُضُوءُ } مُتَّفَقٌ عَلَيْهِ, وَاللَّفْظُ لِلْبُخَارِيّ ِ (88)‏.‏ ‏4 ‏- صحيح.‏ رواه البخاري (132)‏، ومسلم (303)‏، ولفظ مسلم: (منه)‏ بدل (فيه)‏.‏

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also referenced under: Book 1, Hadith 75 (English)