Sunan an-Nasa'i 33
سنن النسائي#33Sahihأَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ أَنْبَأَنَا أَزْهَرُ، أَنْبَأَنَا ابْنُ عَوْنٍ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، عَنْ عَائِشَةَ، قَالَتْ يَقُولُونَ إِنَّ النَّبِيَّ صلى الله عليه وسلم أَوْصَى إِلَى عَلِيٍّ لَقَدْ دَعَا بِالطَّسْتِ لِيَبُولَ فِيهَا فَانْخَنَثَتْ نَفْسُهُ وَمَا أَشْعُرُ فَإِلَى مَنْ أَوْصَى قَالَ الشَّيْخُ أَزْهَرُ هُوَ ابْنُ سَعْدٍ السَّمَّانُ .
It was narrated that 'Aishah said:"They say that the Prophet (ﷺ) made a will for 'Ali,[1] but he called for a basin in which to urinate, then he went flaccid suddenly (and died), so how could he leave a will?!" The Shaikh said: Azhar (one of the narrators) is Ibn Sa'd As-Samman. [1] Meaning, appointing him as the Khalifah
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: 1:33