It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that he said: I heard the Messenger of Allah (peace and blessings be upon him) saying: "The purification of every hide is in its tanning." I said: O Messenger of Allah! We travel with these non-Arabs who have cooking pots in which they cook carrion and the flesh of swine. He (peace and blessings be upon him) said: "If they are earthenware, boil water in them and then wash them; and if they are of copper, wash them (in the normal way), for water purifies everything." This hadith has an authentic (sahih) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.