Language:
كتاب الوضوء
4  
Ablutions (Wudu')
(67)
Chapter: An-Najasat (impure and filthy things) which fall in cooking butter (ghee - which is obtained by evaporating moisture from butter) and water
(67)
باب مَا يَقَعُ مِنَ النَّجَاسَاتِ فِي السَّمْنِ وَالْمَاءِ
Sahih al-Bukhari 235

Narrated Maimuna:

Allah's Messenger (ﷺ) was asked regarding ghee (cooking butter) in which a mouse had fallen. He said, "Take out the mouse and throw away the ghee around it and use the rest."

حَدَّثَنَا إِسْمَاعِيلُ، قَالَ حَدَّثَنِي مَالِكٌ، عَنِ ابْنِ شِهَابٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنِ ابْنِ عَبَّاسٍ، عَنْ مَيْمُونَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم سُئِلَ عَنْ فَأْرَةٍ سَقَطَتْ فِي سَمْنٍ فَقَالَ ‏ "‏ أَلْقُوهَا وَمَا حَوْلَهَا فَاطْرَحُوهُ‏.‏ وَكُلُوا سَمْنَكُمْ ‏"‏‏.‏
Reference : Sahih al-Bukhari 235
In-book reference : Book 4, Hadith 101
USC-MSA web (English) reference : Vol. 1, Book 4, Hadith 236
  (deprecated numbering scheme)