Is it permissible for a wife to refuse her husband if he requests her presence when the time for prayer is near, whether at the beginning of the marriage or later, out of fear of being late for prayer at its prescribed time due to ghusl (ritual bathing), or out of fear that warm water for ghusl may not be available, which could lead to missing the prayer time?

A wife must obey her husband in matters of intimacy, except for a legitimate Shar'i excuse (such as menstruation, illness, or an obligatory fast). It is not permissible to refuse due to fear of delaying prayer from its early prescribed time, because prayer at the early time is not obligatory, whereas obeying the husband is obligatory. However, if she fears that the prayer time will expire completely, then she is not obliged to obey her husband. It is also not permissible to refuse due to fear of not having warm water available; rather, she should respond to her husband, then perform ghusl or tayammum if she is unable to perform ghusl.