Is expiation (kaffarah) obligatory for someone who insults a Muslim by saying, "May your mother's religion be cursed"?

Cursing religion, or the creed, or Islam is major disbelief (kufr akbar) by the consensus of scholars, and its perpetrator is asked to repent. As for cursing the religion of a Muslim person, such as saying, "May your religion be cursed," it is also disbelief, but some scholars have allowed for the possibility that the intent was the person's state and religiosity, in which case he would be disciplined and punished instead of being declared a disbeliever.

So, whoever intends the Sacred Law (Sharia (definition)) is a disbeliever and apostate who is asked to repent. If he does not show that (intention), then he is a zindiq (heretic/hypocrite) who is to be killed even if he repents. However, if he intended a person's state and religiosity, he is to be disciplined. Whoever curses religion or a madhhab (definition) (school of thought) commits disbelief and deserves to be killed if he does not repent, because cursing religion is more severe than belittling it.

The expiation for cursing is sincere repentance, along with the curser deserving punishment and discipline.