Is it permissible for the husband to fast on behalf of his wife for the missed days of Ramadan that she owes, if she is unable to fast them due to illness?

If the wife is unable to make up the days due to an illness from which recovery is hoped, then she should postpone the make-up until she recovers. However, if her illness is one from which recovery is not hoped, then she must feed a poor person for each day. It is not permissible for the husband to fast on her behalf.