What are the hadiths indicating the obligation to kill one who insults the Prophet, peace and blessings be upon him, even if he repents? And is there a hadith stating that his repentance is not accepted, or is it an inference that his killing is a right specific to him that cannot be pardoned?

Muslims have unanimously agreed on the disbelief of anyone who insults Allah or His Messenger (peace be upon him), and scholars have concurred that the punishment for one who insults the Messenger is death. The Sunnah also indicates that the blood of one who insults the Prophet (peace be upon him) is to be shed with impunity.

Scholars have differed on whether the repentance of the slanderer is accepted. Some have held that anyone who insults the Prophet (peace be upon him) must be killed in all circumstances, even if he repents sincerely, because his insult involves two rights: a right of Allah and a right of a human being.

While others have favored accepting the repentance of the slanderer if he repents sincerely, as repentance erases all sins, even associating partners with Allah.