With the Hadith
Killing those who explicitly insult the Prophet, peace and blessings be upon him
Narrated by Ibn Abbas, may God be pleased with him: "A blind man had a slave woman who used to insult the Prophet, may God bless him and grant him peace, and speak ill of him. He forbade her, but she did not stop, and he rebuked her, but she did not desist. He said: One night, she began to speak ill of the Prophet, may God bless him and grant him peace, and insult him. So he took a dagger, placed it in her stomach, and leaned on it until he killed her. A child fell between her legs and was stained with blood. When morning came, this was mentioned to the Messenger of God, may God bless him and grant him peace. He gathered the people and said: I adjure by God any man who has done what he has done and to whom I owe a right, let him stand up. The blind man stood up, stumbling through the people until he sat before the Prophet, may God bless him and grant him peace, and said: O Messenger of God, I am her owner. She used to insult you and speak ill of you. I forbade her, but she did not stop, and I rebuked her, but she did not desist. I have two sons from her like two pearls, and she was my companion. Last night, she began to insult you and speak ill of you. So I took a dagger, placed it in her stomach, and leaned on it until I killed her. The Prophet, may God bless him and grant him peace, said: "Bear witness that her blood is worthless." Narrated by Abu Dawood and Al-Nasa'i, and Ahmad used it as evidence.
Imam Al-Shawkani, may God have mercy on him, said in Al-Nil: In the hadith of Ibn Abbas, there is evidence that whoever insults the Prophet, peace and blessings be upon him, is to be killed. Ibn al-Mundhir narrated the consensus that whoever explicitly insults the Prophet, peace and blessings be upon him, must be killed. Abu Bakr al-Farisi, one of the imams of the Shafi'i school, narrated in the book of Ijma' (Consensus) that whoever insults the Prophet, peace and blessings be upon him, with explicit slander, has disbelieved according to the consensus of scholars. Even if he repents, the killing will not be waived because the punishment for his slander is killing, and the punishment for slander is not waived by repentance. Al-Khattabi said: I know of no disagreement on the obligation to kill him if he is a Muslim.
As for those who insult the Prophet, peace and blessings be upon him, from the people of covenant and protection, Ibn al-Qasim said, narrating from Malik: Whoever insults the Prophet, peace and blessings be upon him, from them is to be killed unless he converts to Islam. Ibn al-Mundhir narrated the same from Al-Layth, Al-Shafi'i, Ahmad, and Ishaq.
As for the Prophet, peace and blessings be upon him, not killing the Jews who used to say to him, "As-Samu 'alaykum" (death be upon you), it is because they were not proven guilty of that, nor did they confess to it, so he did not judge them based on his knowledge. It was said that since they did not make it apparent and twisted it with their tongues, he refrained from killing them. In any case, the disbelief of the Jews is severe, and their blood was only spared due to the covenant. The covenant does not and will never imply that they can insult the Prophet, peace and blessings be upon him. Whoever insults him from them or from others, such as Christians and other religions of disbelief, has violated the covenant, and it is nullified. He becomes a disbeliever without a covenant, so his blood is worthless and he must be killed.
What the disbelievers are doing today in violating the sanctity of the Prophet, peace and blessings be upon him, and offending him, is only the implementation of a plan set by the countries of Europe and America that aims to ignite the spirit of Crusader hatred among their peoples against Islam after they have realized and felt that Islam is sweeping away their barriers and penetrating the heart of their homes, so those who are guided from their peoples embrace Islam, and that Islam is the natural and innate alternative to their corrupt beliefs, their rotten democracy, and their savage capitalism. The coming state of Islam, God willing, is the one that will forcefully carry out the message of Islam to them and to the entire world in a practical way, and it is the one that will avenge those who offended our Prophet, peace be upon him. {And those who have wronged will know to what [kind of] return they will be returned.}