I say, and with God's success: If oil becomes impure and is made into soap, it purifies; the Prophet (peace be upon him) was asked about a mouse that dies in ghee, and he said: "If it is solid, throw away the mouse and what is around it, and eat the rest; but if it is liquid, do not." In Sahih al-Bukhari 5: 2105, and in another narration: "It can be benefited from but not eaten," in Sunan al-Bayhaqi al-Kabir 9: 354, and Sunan al-Daraqutni 4: 291. Likewise, wine becomes pure when it turns into vinegar, and similarly, a pig or a donkey that falls into salt and becomes salt, and also excrement when buried in a place and turns to ash. Through transformation, musk becomes pure and fragrant, although it is originally the blood of a deer; as narrated by al-Tirmidhi from Abu Sa'id al-Khudri (may Allah be pleased with him) who said: The Messenger of Allah (peace be upon him) said: "The best of perfumes is musk." Ambergris and civet — which is filth that accumulates under the tail of a cat — also become pure through transformation. All of these become pure through transformation due to the change of their essence and their becoming something else. Refer to: Al-Hidayah 1: 37, Fath al-Qadir 1: 176, Radd al-Muhtar 6: 735, Al-Bahr al-Ra'iq 1: 239, 8: 546, Al-Binayah 1: 755, Risail al-Arkan p. 48, Fatawa al-Tatar Khaniyyah q. 65/b, Naf' al-Mufti p. 143, and Allah knows best.