وَعَنْ رَجُلٍ صَحِبَ
اَلنَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ (قَالَ: «نَهَى رَسُولُ اَللَّهِ) صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ -«أَنْ تَغْتَسِلَ اَلْمَرْأَةُ بِفَضْلِ اَلرَّجُلِ، أَوْ اَلرَّجُلُ بِفَضْلِ اَلْمَرْأَةِ، وَلْيَغْتَرِفَا جَمِيعًا»
The Messenger of Allah (sallallahu alayhi wa sallam) 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.
Bulugh al-Maram 8, Book 1, The Book of Purification, Hadith 8. 1 min read