Praise be to Allaah.
It is haraam (forbidden) for a man to have intercourse with
his wife during her period.
Allaah says (interpretation of the meaning):
“They ask you concerning menstruation. Say: that is an
Adha (a harmful thing for a husband to have a sexual intercourse with his wife
while she is having her menses), therefore, keep away from women during menses
and go not unto them till they are purified (from menses and have taken a bath)”
[al-Baqarah 2:222].
So it is not permissible for a man to have intercourse with
his wife until she has become pure and has taken a bath (made ghusl), because
Allaah says (interpretation of the meaning):
“And when they have purified themselves, then go in unto
them as Allâh has ordained for you (go in unto them in any manner as long as
it is in their vagina).” [al-Baqarah 2:222]
Another indication of how abhorrent this sin
is, is the words of the Prophet (peace and blessings
of Allaah be upon him): “Whoever has intercourse with a menstruating woman,
or has anal intercourse with a woman, or goes to a fortune-teller, has disbelieved
in what was revealed to Muhammad.” (Narrated by al-Tirmidhi from
Abu Hurayrah, 1/243; see also Saheeh al-Jaami’, 5918).
So you have to prevent him and stop him from
doing that. If you obey him in this matter then you will be a partner in the
sin with him, but if he forces you to do it then the sin will be on him.please
see Question #2121 And Allaah knows best.