Is it permissible for a man married to two women, if he wishes to have intercourse with his first wife and she is menstruating, to have intercourse with his second wife on her night?

The scholars are unanimous on the obligation of justice in dividing time among wives. The basic principle is that the division of the night should be followed by the day. It is not permissible for the husband to enter the house of a wife who is not on duty at night, except in cases of extreme necessity. As for entering during the day, it is permissible only out of need, provided that he does not have intercourse with anyone other than the wife on duty. This ruling also includes the menstruating wife, for she has a right to the division of time, and her menstruation does not negate her right. It is permissible for the husband to enjoy his menstruating wife during her turn, without engaging in vaginal intercourse.