Musannaf Ibn Abi Shayba 16:177

Abu Bakr (Matar) narrated to us, he said: Ghundar narrated to us, from Shu'bah, from Simak, from Ikrimah, from Ibn Abbas: He was asked about a mouse that fell into solidified ghee. He ordered that it be thrown away along with what was around it, and that the rest of it be eaten.