Sahih Muslim 2175
The Book of Prayer - Funerals
وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا هُشَيْمٌ، عَنْ خَالِدٍ، عَنْ حَفْصَةَ بِنْتِ سِيرِينَ، عَنْ أُمِّ عَطِيَّةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم حَيْثُ أَمَرَهَا أَنْ تَغْسِلَ ابْنَتَهُ قَالَ لَهَا " ابْدَأْنَ بِمَيَامِنِهَا وَمَوَاضِعِ الْوُضُوءِ مِنْهَا " .
Umm 'Atiyya reported that when the Messenger of Allah (ﷺ) asked her to wash his daughter, he told her to start from the right side, and with those parts of the body over which Wudu' is performed
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.