Short answer
No. No Muslim may punish anyone himself, for blasphemy or for any other crime. In Islamic law, punishment belongs only to a lawful court, after proof and a fair trial. Scholars agree that even a murderer may be punished only by lawful authority. An accused person may be innocent, or may have been misheard. A man who kills on his own kills someone no court has found guilty. The Qur'an says killing a believer on purpose earns Hell. The Prophet (ﷺ) said whoever kills a non-Muslim living under a treaty will not smell Paradise. Wherever a Muslim lives, he must keep that country's law (17:34). So such a man faces a murder charge in this world, and God's (﷾) judgement in the next. The Prophet (ﷺ) himself bore insults with patience.
Full explanation
Punishment belongs to a court, not to a person
Al-Qurtubi, a 13th-century scholar of the Qur'an, records a point on which the scholars agree. Even retaliation for murder is carried out only by those in lawful authority. Individuals may not take it for themselves. Ibn Qudamah, a 12th-century jurist, says no one may carry out a fixed penalty except the ruler or his deputy. If a man may not punish a killer himself, he may still less punish someone for words. The Qur'an tells Muslims to refer disputes to Allah (﷾), His Messenger (ﷺ) and those in authority. And a Muslim in any country is bound by his promise to keep its laws (17:34).
Al-Qurtubi records that the scholars do not differ that retaliation for killing is carried out only by those in lawful authority, and that individuals may not take it for themselves.
Ibn Qudamah, a Hanbali jurist, holds that, as a rule, no one may carry out a fixed penalty (hadd) except the ruler (imam) or the one he appoints to act for him. The only exception he allows is an old ruling on a master and his own slave, which has no application today.
“O ye who believe! Obey Allah, and obey the Messenger, and those charged with authority among you. If ye differ in anything among yourselves, refer it to Allah and His Messenger, if ye do believe in Allah and the Last Day: That is best, and most suitable for final determination.”
“Come not nigh to the orphan's property except to improve it, until he attains the age of full strength; and fulfil (every) engagement, for (every) engagement will be enquired into (on the Day of Reckoning).”
No one is guilty until it is proven
The Qur'an says: if a wicked person brings you news, "ascertain the truth, lest ye harm people unwittingly". It even punishes those who accuse a woman of adultery without four witnesses. It forbids saying to anyone who offers peace, "Thou art none of a believer". In a battle, Usama killed a man who had just said there is no god but Allah (﷾). He thought the man said it only to save himself. The Prophet (ﷺ) asked him again and again how he could do it (Bukhari 4269). No one may judge another's heart and kill him for it.
“O ye who believe! If a wicked person comes to you with any news, ascertain the truth, lest ye harm people unwittingly, and afterwards become full of repentance for what ye have done.”
“And those who launch a charge against chaste women, and produce not four witnesses (to support their allegations),- flog them with eighty stripes; and reject their evidence ever after: for such men are wicked transgressors;-”
“O ye who believe! When ye go abroad in the cause of Allah, investigate carefully, and say not to any one who offers you a salutation: "Thou art none of a believer!" Coveting the perishable goods of this life: with Allah are profits and spoils abundant. Even thus were ye yourselves before, till Allah conferred on you His favours: Therefore carefully investigate. For Allah is well aware of all that ye do.”
Usama ibn Zayd reports that in a battle he killed a man after the man had said "There is no god but Allah", thinking he said it only to save himself. The Prophet (ﷺ) asked again and again: did you kill him after he said there is no god but Allah? Usama said he wished he had not been a Muslim before that day.
Someone is accused of insulting the Prophet (ﷺ) or the faith.
May a Muslim punish him himself?
No. Punishment belongs only to a lawful court, after proof and a fair trial.
Could the accusation be wrong?
Yes. He may be innocent or misheard. The Qur'an says: ascertain the truth.
And a man who kills on his own?
He kills someone no court has found guilty. He faces a murder charge in this world, and God's (﷾) judgement in the next.
What did the Prophet (ﷺ) do with insults?
He bore them with patience. Answer with what is better.
What awaits a man who kills on his own
The Qur'an says: "If a man kills a believer intentionally, his recompense is Hell". It says killing one innocent person is like killing all mankind. The Prophet (ﷺ) said whoever kills a non-Muslim under a treaty will not smell the fragrance of Paradise (Bukhari 3166). He also said a believer is safe in his faith until he sheds blood unlawfully (Bukhari 6862). In this world, the law of the land will try him for murder. Islam does not shield him.
“If a man kills a believer intentionally, his recompense is Hell, to abide therein (For ever): And the wrath and the curse of Allah are upon him, and a dreadful penalty is prepared for him.”
“On that account: We ordained for the Children of Israel that if any one slew a person - unless it be for murder or for spreading mischief in the land - it would be as if he slew the whole people: and if any one saved a life, it would be as if he saved the life of the whole people. Then although there came to them Our messengers with clear signs, yet, even after that, many of them continued to commit excesses in the land.”
Abdullah ibn Amr reports that the Prophet (ﷺ) said that whoever kills a person who has a treaty with the Muslims will not smell the fragrance of Paradise, though its fragrance reaches a distance of forty years.
Ibn Umar reports that the Prophet (ﷺ) said a believer keeps room in his religion as long as he does not shed blood unlawfully.
How the Prophet (ﷺ) answered insults
Some men greeted the Prophet (ﷺ) with "death be upon you". His wife Aisha cursed them back. He told her to be gentle, and answered them only with "and upon you" (Bukhari 6030). A Bedouin once pulled his cloak so hard it marked his neck, and demanded money. He smiled and gave him something (Bukhari 3149). When the people of Ta'if drove him out, an angel offered to crush them. He refused, hoping that Allah (﷾) would bring from their children people who worship Him alone (Bukhari 3231).
Aisha reports that some men greeted the Prophet (ﷺ) with "death be upon you" in place of "peace be upon you". She cursed them back. The Prophet told her to be calm, to be gentle and to avoid harshness and foul words. He had answered them only with "and upon you".
Anas reports that a bedouin pulled the Prophet's (ﷺ) cloak so roughly that its hem left a mark on his shoulder, and demanded to be given some of the wealth Allah had given him. The Prophet turned to him, smiled, and ordered that he be given a gift.
Aisha asked the Prophet (ﷺ) whether he had known a day harder than Uhud. He named the day he presented his call to Ibn Abd Yalil, a chief of Ta'if, and was turned away. As he left in sorrow, Gabriel came with the Angel of the Mountains, who offered to let the two great mountains fall on those who had rejected him. The Prophet refused and said he hoped that their descendants would worship Allah alone.
Blasphemy laws around the world
Many countries have laws against blasphemy. In 2019, 79 of 198 countries and territories had them, including some in Europe. England and Wales abolished theirs only in 2008. Where such a law exists, it is a matter for the courts, with evidence and a trial. No country and no school of Islamic law lets a crowd or a single man carry out a sentence.
In 2019, 79 of 198 countries and territories (40%) had laws or policies against blasphemy, including some in Europe, and 22 had laws against apostasy.
Abolished the common-law offences of blasphemy and blasphemous libel in England and Wales.
Al-Qurtubi records that the scholars do not differ that retaliation for killing is carried out only by those in lawful authority, and that individuals may not take it for themselves.
Answer with something better
The Qur'an tells Muslims: "Repel (Evil) with what is better". Then an enemy may become "as it were thy friend and intimate". It forbids insulting the gods of others, so that they do not insult Allah (﷾) in return. The Prophet (ﷺ) said: make things easy, and do not drive people away (Bukhari 69). A Muslim who kills over words drives people away from Islam. One who answers with patience draws them to it.
“Nor can goodness and Evil be equal. Repel (Evil) with what is better: Then will he between whom and thee was hatred become as it were thy friend and intimate!”
“Revile not ye those whom they call upon besides Allah, lest they out of spite revile Allah in their ignorance. Thus have We made alluring to each people its own doings. In the end will they return to their Lord, and We shall then tell them the truth of all that they did.”
Anas ibn Malik reports that the Prophet (ﷺ) said: make things easy for people and do not make them hard; give them good news and do not drive them away.
Perspectives
Islam tells Muslims to kill blasphemers
Some critics say that people who kill for blasphemy are only doing what Islam commands.
Classical Islamic law gave death as the penalty for insulting the Prophet (ﷺ).
Rebuttal
Where classical law set a penalty, only a lawful court in a Muslim state could give it, after a trial. Scholars agree that individuals may not carry out punishments themselves. A man who kills on his own breaks Islamic law. And Muslims keep the law of the country they live in.
The Prophet (ﷺ) ordered the killing of Ka'b ibn al-Ashraf for his poems.
Rebuttal
Ka'b was not killed for words alone. In a time of war he went to Mecca and urged the Quraysh to fight Medina again. The order came from the Prophet (ﷺ) as head of state and judge of Medina. No private person may copy it.
The Islamic perspective
Only a lawful court may punish, after proof and a fair trial. A Muslim who kills on his own commits murder, a grave sin. He must answer for it in this world and the next. The Prophet (ﷺ) answered insults with patience.
Scholars agree that even retaliation for murder is carried out only by lawful authority.
The Qur'an says killing a believer on purpose earns Hell.
Whoever kills a non-Muslim under a treaty will not smell the fragrance of Paradise.
The Prophet (ﷺ) answered those who cursed him with gentleness.
Muslims must keep the law of the country they live in.