Is it permissible for a wife to refuse her husband's request for intimacy if she fears missing the prayer, especially the Fajr prayer?

If a man calls his wife to his bed, she must obey him, for the Prophet, peace and blessings be upon him, said: "If a man calls his wife to his bed and she refuses, and he spends the night angry with her, the angels curse her until morning." Sleeping before the prayer time begins is not forbidden, even if it leads to missing the prayer, because the مكلف (accountable person) has not yet been addressed by the prayer obligation before its time. As for sleeping after the prayer time has begun, if one knows or believes that he will remain asleep until the time expires, then it is not permissible unless he has entrusted someone he trusts to wake him up. Some Shafi'is held the view that it is forbidden to sleep before the prayer time if one believes he will not wake up. Therefore, it is obligatory for the wife to obey her husband and strive to wake up for prayer by using an alarm clock or similar means.