Is it permissible to offer the Fajr prayer half an hour before its prescribed time due to an extreme necessity, such as entering a long surgical operation?

Prayer is not valid before its prescribed time, as Allah Almighty says: "Indeed, prayer has been decreed upon the believers a book [due at] fixed times." Whoever prays before its time must repeat it. It is also not permissible to delay prayer beyond its time. A conscious sick person prays according to their condition, as Allah Almighty says: "So fear Allah as much as you are able." As for someone who has lost consciousness, such as one who has fainted, some scholars obligate them to make up the prayers, while others do not.