Is it permissible for a man to have intercourse with his wife while she is menstruating, and what is the expiation for a man having anal intercourse with his wife without knowing of its prohibition?

It is not permissible for a man to have intercourse with his wife while she is menstruating, due to the Almighty’s saying: "So keep away from women during menstruation." And it is not permissible for him to have anal intercourse with her, due to the Almighty’s saying: "So approach them from where Allah has commanded you," and the Prophet's (PBUH) saying: "Cursed is he who has intercourse with his wife in her anus." Whoever does this must repent sincerely and seek forgiveness.