Sahih al-Bukhari 178
صحيح البخاري#178Sahihحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، عَنْ مُنْذِرٍ أَبِي يَعْلَى الثَّوْرِيِّ، عَنْ مُحَمَّدٍ ابْنِ الْحَنَفِيَّةِ، قَالَ قَالَ عَلِيٌّ كُنْتُ رَجُلاً مَذَّاءً، فَاسْتَحْيَيْتُ أَنْ أَسْأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم فَأَمَرْتُ الْمِقْدَادَ بْنَ الأَسْوَدِ فَسَأَلَهُ فَقَالَ " فِيهِ الْوُضُوءُ ". وَرَوَاهُ شُعْبَةُ عَنِ الأَعْمَشِ.
Narrated `Ali:I used to get emotional urethral discharges frequently and felt shy to ask Allah's Messenger (ﷺ) about it. So I requested Al-Miqdad bin Al-Aswad to ask (the Prophet (ﷺ) ) about it. Al-Miqdad asked him and he replied, "One has to perform ablution (after it)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 4:44