The Cleansing of Impurities - Section 2 Mishkat al-Masabih 511
Translation
Salma b. al-Muhabbiq said that on the expedition to Tabuk [In the year 9 A.H.] God’s messenger came to a household, and seeing a bucket hanging, asked for water. They told him that the animal had died a natural death, but he replied, “Its tanning is its purification.” Ahmad and Abu Dawud transmitted it.