Sunan Ibn Majah, Volume 2, Book 6, Hadith 1626 (DarusSalam) ⓘ

It was narrated that Aswad said: “They said in ‘Aishah’s presence that ‘Ali was appointed (by the Prophet before he died), and she said: ‘When was he appointed? He (the Prophet) was resting against my bosom, or in my lap, and he called for a basin, then he became limp in my lap and died, and I did not realize it. So when did he appoint him?’”

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا إِسْمَاعِيلُ ابْنُ عُلَيَّةَ، عَنِ ابْنِ عَوْنٍ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، قَالَ ذَكَرُوا عِنْدَ عَائِشَةَ أَنَّ عَلِيًّا كَانَ وَصِيًّا ‏.‏ فَقَالَتْ مَتَى أَوْصَى إِلَيْهِ فَلَقَدْ كُنْتُ مُسْنِدَتَهُ إِلَى صَدْرِي - أَوْ إِلَى حِجْرِي فَدَعَا بِطَسْتٍ فَلَقَدِ انْخَنَثَ فِي حِجْرِي فَمَاتَ وَمَا شَعَرْتُ بِهِ فَمَتَى أَوْصَى ـ صلى الله عليه وسلم ـ ‏.‏