The Messenger of Allah ﷺ said, "Whoever washes a deceased person should perform a full bath himself."
حدثنا محمد بن عبد الملك بن أبي الشوارب حدثنا عبد العزيز بن المختار عن سهيل بن أبي صالح عن أبيه
قال رسول الله ﷺ من غسل ميتا فليغتسل
No references are available.
[Sahih] Reported by Tirmidhi, in the Book of Funerals, Chapter on What Has Been Said Regarding ghusl for One Who Has Washed the Deceased, and it has another hasan route with Abu Dawud, no. 993, from Muhammad bin Abdul-Malik, and he said, hasan, no. 3162, and elsewhere. It has many supporting narrations, including one reported by Bayhaqi, and its chain is hasan.