Musnad Ahmad 30:3225

Muhammad ibn Ja‘far narrated to us, he said: Ma‘mar narrated to us, he said: Ibn Shihab informed us, from Ibn al-Musayyib, from Abu Hurayrah, who said: The Messenger of Allah, peace and blessings of Allah be upon him, was asked about a mouse that fell into ghee and died. He said: "If it is solid, take it and what is around it, and eat what remains. But if it is liquid, do not eat it."