Sunan Ibn Majah, Book 1, Hadith 401 (In-Book) ⓘ

It was narrated from Ibn 'Abbas that: One of the wives of the Prophet took a bath to cleanse herself from sexual impurity, then the Prophet performed ablution and had a bath with the water left over from her ablution."

حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَكِيعٌ، عَنْ سُفْيَانَ، عَنْ سِمَاكِ بْنِ حَرْبٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ امْرَأَةً، مِنْ أَزْوَاجِ النَّبِيِّ ـ صلى الله عليه وسلم ـ اغْتَسَلَتْ مِنْ جَنَابَةٍ فَتَوَضَّأَ أَوِ اغْتَسَلَ النَّبِيُّ ـ صلى الله عليه وسلم ـ مِنْ فَضْلِ وَضُوئِهَا ‏.‏