What is the ruling on using manufactured leather in lands where most of the people are disbelievers and their slaughtered animals are considered carrion, and is it true that it was reported from Ali and Ibn Mas’ud, may Allah be pleased with them, that the hide of an animal whose meat is permissible to eat becomes pure by tanning?

A group of scholars, other than An-Nawawi, mentioned that the opinion of the purity of all dead animals' skins by tanning—except for the pig and the dog—was attributed to Ali and Ibn Mas'ud. Several narrations support this, among them what Ibn al-Mundhir reported from Ibn Mas'ud, who said: "Its purification is its tanning," and from Ali: "The purification of skins is their tanning." There are other narrations, both Marfu' (attributed to the Prophet) and Mawquf (attributed to a Companion), in the books of Hadith (definition) and Sunnah (definition). The preponderant opinion is the purity of the dead animal's skin by tanning, due to the ease and alleviation it provides.