I heard the Messenger of Allah ﷺ say, "Any hide that has been tanned has become pure."
حدثنا سفيان عن زيد بن أسلم عن ابن وعلة
سمعت رسول الله ﷺ يقول أيما إهاب دبغ فقد طهر
Its chain of transmission is sahih. Ibn Waalah is Abdul-Rahman bin Waalah Sabai Misri, and he is a trustworthy Tabii. The hadith was also narrated by Muslim, Tirmidhi, and Ibn Majah, as in Muntaqa 86. In Tahdhib, in the biographical entry on Ibn Waalah, it mentions that Ahmad noted him and declared him daif regarding the hadith on tanning. Ihab means the hide before it is tanned. It will come at greater length at 2435 and 2522.