A mouse fell into the butter-fat and died. The Prophet (ﷺ) was asked about that. He said, "Throw away the mouse and the butter-fat that surrounded it, and eat the rest of the butter-fat (As-Samn).
Sahih al-Bukhari Book 72, Hadith 63
← Previous Hadith Allah's Messenger (ﷺ) and I entered the house of Maimuna. A roasted mastigure was served. Allah's Messenger (ﷺ) stretched his hand out (to eat of it) but some woman said, "Inform Allah's Messenger (ﷺ) of what he is about to eat." So they said, "It is mastigure, O Allah's Messenger (ﷺ)!" He withdrew his hand, whereupon I said, "O Allah's Messenger (ﷺ)! Is it unlawful?" He said, "No, but this is not found in the land of my people, so I dislike it." So I pulled the mastigure towards me and ate it while Allah's Messenger (ﷺ) was looking at me.

Sahih al-Bukhari Book 72, Hadith 62 Next Hadith → regarding an animal, e.g., a mouse or some other animal that had fallen into solid or liquid oil or butter-fat: I had been informed that a mouse had died in butter-fat whereupon Allah's Messenger (ﷺ) ordered that the butter-fat near it be thrown away and the rest of the butter-fat can be eaten.

Sahih al-Bukhari Book 72, Hadith 64