Must a wife obey her husband who refuses to let her wear the niqab and threatens to divorce her if she does so?

It is not permissible for a husband to prevent his wife from covering her face, and it is not permissible to obey him in that. The husband should be reminded of Allah and the Last Day, and someone from his family or others should be interceded to convince him. If he does not respond, then the wife must adhere to obedience to Allah, even if the husband threatens her with divorce or it occurs. For whoever fears Allah, He will make for him a way out and provide for him from where he does not expect.