Musannaf Ibn Abi Shayba 35:300

Zayd ibn al-Hubab narrated to us, from Malik ibn Anas, from Ishaq ibn Abdullah ibn Abi Talha al-Ansari, from Humayda bint Ubayd ibn Rifa'a, from Kabsha bint Ka'b—who was married to one of the children of Abu Qatada—that she poured water for Abu Qatada to perform ablution. A cat came to drink, so he tilted the vessel for it. We began to look, and he said, "O daughter of my brother, are you surprised?" He said, "The Messenger of Allah (peace and blessings of Allah be upon him) said: 'It is not impure; it is among those who roam about among you, or among those who roam about.'"