I met a man who had accompanied the Prophet ﷺ for four years, just as Abu Hurairah had accompanied him. He said, "The Messenger of Allah ﷺ forbade that a woman bathe with the leftover water of a man or that a man bathe with the leftover water of a woman."Musaddad added, "Rather, let them both scoop from it together."
حدثنا أحمد بن يونس حدثنا زهير عن داود بن عبد الله ح و حدثنا مسدد حدثنا أبو عوانة عن داود بن عبد الله
لقيت رجلا صحب النبي ﷺ أربع سنين كما صحبه أبو هريرة قال نهى رسول الله ﷺ أن تغتسل المرأة بفضل الرجل أو يغتسل الرجل بفضل المرأة زاد مسدد وليغترفا جميعا
Its isnad is sahih. Nasai narrated it in his chapter on Purification, in the section on the prohibition of washing with the leftover water of a person in a state of major ritual impurity (janabah), Hadith: 239, from the hadith of Abu Awana Waddah bin Abdullah, with this chain. Hafiz [Ibn Hajar] graded it sahih in Bulugh Maram, Hadith: 6 (in my edition).