Musannaf Ibn Abi Shayba 1:329

Abu al-Ahwas narrated to us, from Simak, from a man from the people of Medina, who said: Water for purification was placed for Abdullah ibn Umar, and a cat drank from it. Then Abdullah came to perform ablution from it, and it was said to him: "The cat has drunk from it." He said: "It is only one of the household."