Hadithcore
Bulugh al-Maram, 552

Asma’ bint ’Umais (RAA) narrated that Fatimah (RAA) (the daughter of the prophet (ﷺ) made a will that ‘Ali (RAA) was to wash her when she dies.’ Related by Ad-Daraqutni.

وَعَنْ أَسْمَاءَ بِنْتِ عُمَيْسٍ رَضِيَ اَللَّهُ عَنْهَا: { أَنَّ فَاطِمَةَ عَلَيْهَا اَلسَّلَامُ أَوْصَتْ أَنْ يُغَسِّلَهَا عَلِيٌّ رَضِيَ اَللَّهُ تَعَالَى عَنْهُ } رَوَاهُ اَلدَّارَقُطْنِيُّ [1]‏ .‏

References2 variants
In-Book Reference
Book 3, Hadith 20
English Reference
Book 3, Hadith 576