Sunan an-Nasa'i, Volume 1, Book 2, Hadith 326 (DarusSalam) ⓘ
It was narrated from Ibn 'Abbas that one of the wives of the Prophet performed Ghusl from Janabah, and the Prophet performed Wudu' with her leftover water. She mentioned that to him and he said: "Water is not made impure by anything." [1] [1] See the following versions.
أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ الْمُبَارَكِ، عَنْ سُفْيَانَ، عَنْ سِمَاكٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ بَعْضَ، أَزْوَاجِ النَّبِيِّ صلى الله عليه وسلم اغْتَسَلَتْ مِنَ الْجَنَابَةِ فَتَوَضَّأَ النَّبِيُّ صلى الله عليه وسلم بِفَضْلِهَا فَذَكَرَتْ ذَلِكَ لَهُ فَقَالَ " إِنَّ الْمَاءَ لاَ يُنَجِّسُهُ شَىْءٌ " .
also referenced under: Hadith 325 (Reference) & Book 2, Hadith 1 (In-Book)