What is the ruling of the Sharia regarding delaying the ghusl (ritual bath) from night until after the break of dawn for the performance of Fajr prayer, due to a woman's health being harmed by bathing at night?

One must perform ghusl (definition) (ritual bath) to pray Fajr on time. It is not permissible to delay ghusl until sunrise if one is capable of performing it. If there is harm in performing ghusl due to illness, then tayammum (definition) (dry ablution) is obligatory, based on the Almighty’s saying: "And if you are ill or on a journey… then perform tayammum with clean earth" (Al-Ma'idah: 6). One who is unable to use water is like one who cannot find it. The harm must be certain or highly probable, not merely an illusion.