Musnad Ahmad 30:530

Al-Zuhri said: Humayd narrated to me, from Abu Hurayrah, from the Messenger of Allah (peace and blessings of Allah be upon him), who said: "A woman entered the Fire because of a cat. She tied it up, so she neither fed it nor let it loose to eat from the vermin of the earth, until it died." Al-Zuhri said: "That is so that a man does not rely [solely on his deeds], and a man does not despair."