What is the ruling on insulting religion, and what must the perpetrator do if he realizes his mistake?

Insulting religion is major disbelief (kufr akbar) and apostasy from Islam by consensus. So, whoever insults religion, disparages it, or mocks it, or Allah, His verses, and His Messenger, has disbelieved after his faith. The perpetrator of this is asked to repent; if he repents, his repentance is accepted between him and Allah. If he does not repent, he is executed. Some scholars hold that there is no repentance for him, but the more preponderant view is the acceptance of his sincere repentance. However, if the ruler deems it appropriate to execute him as a deterrent to others, there is no harm in that.