Is it permissible to delay performing ghusl from ritual impurity (janabah) until after the time for Fajr prayer has passed, due to fear of performing ghusl late at night, which would lead to not performing Fajr prayer on time, especially with the husband refusing to change the time of intercourse?

Performing prayer on time is an important matter. Allah the Almighty has warned those who neglect it, and everything that leads to delaying prayer beyond its prescribed time is forbidden. This includes delaying the ritual bath (ghusl (definition)) after a state of major ritual impurity (janabah (definition)) if such a delay leads to not performing the prayer on time. Spouses must do one of two things: either perform the ghusl immediately after janabah before sleeping, or take the necessary measures to wake up and catch the prayer on time. If the husband insists on neglecting the prayer, the wife must advise him and withhold herself from him until he abstains.