The Messenger of Allah ﷺ said, "Any hide that has been tanned has become pure."
أخبرنا قتيبة وعلي بن حجر عن سفيان عن زيد بن أسلم عن ابن وعلة
قال رسول الله ﷺ أيما إهاب دبغ فقد طهر
Muslim narrated it in the Book of Menstruation, Chapter on the purification of the skins of dead animals through tanning, hadith 366, from Qutayba with this chain, and it is in Al-Kubra, hadith 4567.