All perfect praise be to Allah. Blessings and peace be upon Prophet Mohammad.
It is impermissible for anyone to mock religion, and cursing the religion of things is forbidden as well since such an act shakes the status of religion in the heart of the one who repeats such words. In principle, religion must be protected against any act of mockery and those who commit it must be reprimanded and prohibited from doing it again. Moreover, it doesn`t befit a Muslim to utter such words so that his/her tongue doesn`t get used to them since: "A Muslim shouldn`t be a curser, a slanderer or obscene or vulgar. { At-Tirmizi}. Also, the Prophet {PBUH} said: “a slave (of Allah) may utter a word (carelessly) which displeases Allah without thinking of its gravity and because of that he will be thrown into the Hell-Fire.“ {Bukhari}.
Almighty Allah Has Forbidden us from cursing false Gods and religions so as not to incite disbelievers to curse Islam in return since this can be a door way to a great evil. Allah Says in the Holy Quran: “Do not revile those whom they call upon, besides God, lest they then revile God out of spite, through ignorance. So, We have adorned for every community their deeds; then to their Lord they shall return, and He will tell them what they used to do. “ {Al-Annam/108}. The same applies to cursing the religion of ” things or work” because all creatures of Allah are equal in the principle of believing in Him as the one and only God to be worshipped.
Consequently, if the above heinous act was a slip of a tongue on the part of the curser, then it is considered from the false and forbidden utterances, thus he/she must repent and seek forgiveness so as to be acquitted before Allah. However, if he had committed that act to mock Islam-God forbid- then his faith is at stake, thus he must preserve the integrity of his faith and creed, and must abandon uttering such words immediately, make repentance and seek forgiveness. And Allah Knows Best.
* We already have clarified the case of being in apostasy state regarding the one who curses Allah, or the Religion of Islam in Fatwas No. (611) , (2751).