What is the ruling on a husband anally penetrating his wife?

There is no specific prescribed punishment (Hadd) for one who has anal intercourse with his wife, but he should be disciplined (ta'zeer) and commanded to desist from this abhorrent act. His wife is not permitted to obey him, and if she does obey him, she too should be disciplined. If they do not desist after being disciplined, they should be separated.