"The Prophet was asked about the hides of dead animals." He said: "Tanning it purifies it."
Sunan an-Nasa'i Book 41, Hadith 23
← Previous Hadith during the campaign of Tabuk, the Prophet of Allah called for water from a woman. She said: "I only have a waterskin of mine made from an (unslaughtered) dead animal." He said: "Didn't you tan it?" She said: "Of course." He said: "Then it's tanning is its slaughter". (Daif)

Sunan an-Nasa'i Book 41, Hadith 22 Next Hadith → "The Messenger of Allah was asked about the hides of dead animals." He said: "Tanning it purifies it."

Sunan an-Nasa'i Book 41, Hadith 24