Fox fur is not made pure by tanning
Question

Does a fox’s skin become pure after tanning it? Is it permissible to use it as cloth or anything else? Is it permissible to buy, sell, and trade in it?.
Praise be to Allah.The skin of the fox, like its flesh, is najis, because it is a wild animal and is included in the general prohibition because of the hadeeth of Abu Hurayrah (may Allaah be pleased with him), according to which the Messenger of Allaah (blessings and peace of Allaah be upon him) said: “It is haraam to eat any wild animal that has fangs.” Narrated by Imam Muslim (may Allaah have mercy on him). And there is the hadeeth of Abu’l-Maleeh ibn Usaamah from his father (may Allaah be pleased with them both) which says that the Messenger of Allaah (blessings and peace of Allaah be upon him) forbade the skins of wild animals. Narrated by Imam Ahmad, Abu Dawood, al-Nasaa’i and al-Tirmidhi, who added: to be used for furnishing. Mu’aawiyah ibn Abi Sufyaan (may Allaah be pleased with him) narrated that he said to a group of the companions of the Prophet (blessings and peace of Allaah be upon him): Do you know that the Messenger of Allaah (blessings and peace of Allaah be upon him) forbade riding on the skins of tigers? They said: Yes, by Allaah. Narrated by Imam Ahmad and Abu Dawood. And it was narrated from al-Miqdaad ibn Ma’di Yakrib (may Allaah be pleased with him) that he said to Mu’aawiyah: I adjure you by Allaah, do you know that the Messenger of Allaah (blessings and peace of Allaah be upon him) forbade wearing the skins of wild animals or riding upon them? He said: Yes. Narrated by Abu Dawood and al-Nasaa’i. And it was narrated from Abu Hurayrah (may Allaah be pleased with him) that the Prophet (blessings and peace of Allaah be upon him) said: “The angels do not accompany any group with whom there is a tiger skin.” Narrated by Abu Dawood. These texts forbid the use of skins from any animals whose meat cannot be eaten, because they are only used for adornment and showing off . 
And Allaah is the source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and Companions.