That the Messenger of Allah (ﷺ) said: "Any skin tanned, then it has been made pure."

This Hadith is Hasan Sahih. This is acted upon according to most of the people of knowledge, they say that when the skin of a dead animal has been tanned then it has been made pure.

[Abu 'Eisa said:] Ash-Shafi'i said: "Any dead animals skin that is tanned, then it has been made pure, except for the dog and the pig." Some of the people of knowledge among the Companions of the Prophet (ﷺ) disliked skins of predators even when tanned, and this is the view of 'Abdullah bin Al-Mubarak, Ahmad and Ishaq, and they were firm about not wearing them and performing Salat in them. Ishaq bin Ibrahim said: "The saying of the Prophet (ﷺ):'Any skin that is tanned, then it has been made pure' only refers to the skins of animals whose meat is eaten." This is how it was explained by An-Nasr bin Shumail.