Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates from the Messenger of Allah (peace and blessings be upon him) concerning the skin of a carcass; he (peace and blessings be upon him) said: "Indeed, its tanning removes its filth and impurity." Its chain is sahih (authentic).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 50