The Ruling on Declaring a Specific Disbeliever a Disbeliever

Question:
A questioner from Kuwait via the network asks: Is it permissible to declare a specific disbeliever a disbeliever? For example, one who says that the Qur'an has been distorted, or one who says that the Qur'an is not complete. Do we call him a disbeliever while he is still alive and has not retracted his statement?

Answer:
Whoever utters words of disbelief or performs acts of disbelief, such as prostrating to other than Allah, slaughtering for other than Allah, making a vow for other than Allah, insulting Allah, or insulting the Messenger, we declare him a disbeliever and apply the ruling of apostasy to him, because we judge by what is apparent. As for what is in his heart or his final state, only Allah knows that.
But we judge him by his outward appearance and treat him as an apostate. Otherwise, if we did not treat him that way, the hudud (fixed punishments) would not be carried out against anyone. We do not say, "We do not know about his heart, so leave him alone." Allah has not entrusted us with the hearts; He has entrusted us with judging by outward appearances. So whoever displays any of the causes of execution is executed, and his case is left to Allah. Yes.