What is the doctrine of safeguarding the Prophet’s honor, and what is the ruling on a father slandering his daughter according to the Quran, the Sunnah, and the sayings of scholars?

Venerating the Prophet, peace and blessings be upon him, is an obligation upon every Muslim, and harming him is an act of disbelief that expels one from the faith. Deliberately harming the Prophet, peace and blessings be upon him, is considered an act of defiance against Allah and His Messenger and necessitates the fire of Hell. Scholars have unanimously agreed on the disbelief of anyone who falsely attributes lies to the Prophet, doubts his truthfulness, insults him, or belittles him. Harming a daughter is harming her father. This includes slandering the Prophet’s daughter, which harms him and diminishes his status. Therefore, deliberately slandering her is an act of disbelief.