Sunan an-Nasa'i 437
سنن النسائي#437Sahihأَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا خَالِدُ بْنُ الْحَارِثِ، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ أَخْبَرَنِي سُلَيْمَانُ الأَعْمَشُ، قَالَ سَمِعْتُ مُنْذِرًا، عَنْ مُحَمَّدِ بْنِ عَلِيٍّ، عَنْ عَلِيٍّ، - رضى الله عنه - قَالَ اسْتَحْيَيْتُ أَنْ أَسْأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم عَنِ الْمَذْىِ مِنْ أَجْلِ فَاطِمَةَ فَأَمَرْتُ الْمِقْدَادَ فَسَأَلَهُ فَقَالَ " فِيهِ الْوُضُوءُ " .
It was narrated that 'Ali said:"I felt too shy to ask the Messenger of Allah (ﷺ) about Madhi because of Fatimah, so I told Al-Miqdad to ask him, and he said: 'Wudu' (is required) for that
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:
In-book reference: 4:43