Is a wife permitted to refuse her husband's request for anal intercourse, knowing that it is forbidden and that she rejects it?

Anal intercourse is forbidden and a major sin. If the husband imposes this reprehensible act on his wife, the condition is void, and she is not permitted to obey him in it, for obedience is only in what is right and lawful. The wife must advise her husband by clarifying the religious ruling, and if he does not desist, she may refer the matter to a judge and request a divorce, which would then be permissible. Some scholars believe that separation between the spouses is obligatory if they agree to anal intercourse. As for anal sex from the front (vaginal intercourse from behind), there is no harm in it.