(1) باب المياه
A man who accompanied the prophet (ﷺ) narrated:
Allah's Messenger (ﷺ) forbade a women to bathe with the water left over by a man and that a man should not bathe with the water left over by a woman (but instead) they should both take scoopfuls of the water together. [Reported by Abu Da'ud and An-Nasa'i and its chain of narrators is Sahih (authentic)].
Reference: Bulugh al-Maram 7
In-book reference: Book 1, Hadith 8
English translation: Book 1, Hadith 9