Reviling the faith or the religion or Islam is major kufr (disbelief), according to scholarly consensus. The one who does this should be asked to repent. If he repents, all well and good, otherwise he should be executed, Allah forbid. See questions no. 42505 and 65551.
With regard to reviling the religion of a particular Muslim person, such as saying “May your religion be cursed” or “May the religion of your mother be cursed” – if his mother is a Muslim – is also reviling the religion, as appears to be the case, which is kufr as stated above. Some of the scholars suggested that it may be interpreted differently, and that what is referred to is the person and his religious commitment. This may be based on circumstantial evidence. In this case he should be punished and disciplined. In any case he should be asked to repent and the matter should be discussed with him.
It says in al-Mawsoo’ah al-Fiqhiyyah: The fuqaha (jusrists) are unanimously agreed that the one who reviles Islam or the religion of the Muslims is a kafir (disbeliever). As for the one who reviles the religion of a Muslim, the Hanafis said, as mentioned in Jami’ al-Fusooleen: The one who reviles the religion of a Muslim should be denounced as a kafir, but his insult may be understood as referring to that person’s bad attitude and bad treatment of others, not Islam itself [because the word ‘deen’ in the phrase under discussion may refer to one’s religion or to one’s way and conduct], in which case he should not be denounced as a kafir. End quote.
Al-Shaykh ‘Ulaysh al-Maliki said: In it [in al-Barzali] there is another issue, which is if a man ridicules the prayer and people who pray, and many people testify against him, some of whom are credible witnesses and some are not. If it is interpreted as ridiculing the worshippers because he thinks ill of them, then it is to be regarded as reviling the Muslims, so he should be disciplined as the judge sees fit. If it is interpreted as ridiculing the worship itself, the correct view is that this is apostasy, because he has done this openly and many people knew about it, which is different than heresy, and the ruling on apostasy should be applied. End quote.
I say: From this ruling it may be understood that the one who reviles Islam or the religion or a madhhab (school of thought) is that this is often done by some of the dregs of the common folk, such as donkey-drivers, camel-drivers and servants, or it may be done by others. If he was referring to the sharee’ah (religious laws) and the rulings that Allah has prescribed for His slaves on the lips of His Prophet (peace and blessings of Allah be upon him), then he is definitely a kafir. If he does this openly then he is an apostate who should be asked to repent; if he repents, all well and good, otherwise he should be executed. If he does not do it openly then he is a heretic who is to be executed even if he repents.
If he was referring to an individual person and his religious commitment, then this is reviling a Muslim and he should be disciplined as the judge sees fit. The two cases may be differentiated on the basis of confession and circumstantial evidence. Some scholars said that the ruling is the same in the second case as in the first. In al-Badr it is narrated that Bahram said concerning apostasy: If the one who does not pray says to the one who tells him to pray: When you enter Paradise, lock the door behind you – if what he meant is that prayer has no effect on one’s religious commitment then he has apostatized, according to scholarly consensus, but if he meant that the prayer of the speaker has no effect because it does not stop him from committing immoral and evil actions, then there are two views as to whether he is an apostate. End quote.
It is well known that the Holy Quran is also part of the religion, and reviling it is kufr, as was stated by al-Barzali in several places. End quote from Fath al-‘Aliy al-Malik fi’l-Fatwa ‘ala Madhhab al-Imam Malik.
The other possibility that he mentioned may occur rarely, but the basic principle is that cursing a person’s religion is cursing Islam, and no one would do that but a reckless person who is so audacious that he transgresses the sacred limits of Allah and commits this grave evil that may lead to his doom. Because the other possibility is unlikely to be the case when someone utters these words, al-Shaykh ‘Ulaysh (may Allah have mercy on him) did not mention it anywhere else, when he was asked: What do you say about a man who curses the religion of another, and a man who curses his madhhab, or one who says to him, “May Allah curse your madhhab, the madhhab of cats” – are they apostates?
I replied: Praise be to Allah and blessings and peace be upon our master Muhammad the Messenger of Allah (peace and blessings of Allah be upon him). Yes, they are apostates because of saying this, and they deserve to be executed if they do not repent, according to scholarly consensus, because reviling religion or a madhhab is only done by the one who is a kafir, and because it is worse than belittling it which implies kufr, and because it comes under the second category mentioned by Ibn ‘Abd al-Salam, al-Qarafi, Ibn Rushd and others. And Allah, may He be glorified and exalted, knows best, and may Allah send blessings and peace upon our Prophet Muhammad. End quote from Fath al-‘Aliy al-Malik.
The expiation for reviling – whether one reviled the religion or the person – is sincere repentance. If a person repents, Allah will accept his repentance. Otherwise the one who reviled another deserves to be punished and disciplined. Al-Nawawi (may Allah have mercy on him) was asked: What should be done to the one who calls a Muslim a dog or a pig and other bad words. Is he sinning?
He replied: Praise be to Allah. He is sinning and he should be punished, and he has to repent. And Allah knows best. End quote from Fatawa al-Nawawi.
See also question no. 42505 for more information on the repentance of one who reviles the religion.
And Allah knows best.