What is the ruling on slandering the honor of the Noble Messenger, may Allah bless him and grant him peace, and our master Umar ibn al-Khattab, and what is the duty of one who hears that?

Slandering the honor of the Prophet (peace and blessings be upon him) and his Companions is an act of disbelief (kufr), and it is incumbent upon the listener to defend them. Whoever commits such an act must repent sincerely, otherwise, he must be boycotted, based on the words of the Almighty: "And He has already revealed to you in the Book that when you hear the verses of Allah being denied and ridiculed, do not sit with them until they engage in another conversation. Indeed, in that case, you would be like them. Indeed, Allah will gather the hypocrites and disbelievers in Hell all together." One who insults the Prophet (peace and blessings be upon him) is a disbeliever who must be executed. Insulting the Companions is strictly forbidden, and whoever insults the Four Caliphs commits an act of disbelief. The People of the Household (Ahl al-Bayt) praised Abu Bakr and Umar and were pleased with them, and Ali married his daughter Umm Kulthum to Umar, which refutes the claims of those who slander them.