Sunan An-Nasai, Chapter: The Book of Purification

that Abu Qatadah entered upon her, then she narrated the following: "I poured some water for him for Wudu, and a cat came and drank from it, so he tilted the vessel for it to drink." Kabshah said: "He saw me looking at him and said: 'Are you surprised, O daughter of my brother?' I said: 'Yes.' He said: 'The Messenger of Allah (saw) said: They are not impure, rather they are among the males and females (animals) who go around among you." (Sahih)