It was narrated from Ibn 'Abbas (رضي الله عنه) that

One of the wives of the Prophet (ﷺ) did ghusl following janabah. Then the Prophet (ﷺ) came and did ghusl with her left over water. She said: I did ghusl from it. The Messenger of Allah (ﷺ) said: "Nothing makes water najis (impure)."