What is the ruling on declaring a disbeliever to be a disbeliever?

Question:
He says: I heard from some of the brothers that it is not permissible to apply the term "disbelief" to a specific disbeliever. Is this correct?

Answer:
We have only the apparent reality; we judge people based on what appears to us. So, if someone commits an act of disbelief, we judge him to be a disbeliever. If someone commits an act of shirk (associating partners with Allah), we judge him to be a mushrik (one who associates partners with Allah) and treat him as we treat disbelievers and mushriks. As for saying that in the Hereafter he is among the people of the Fire, that is with Allah (Mighty and Majestic); we do not know. Matters of the Hereafter are with Allah. As for matters of this world, we judge him based on the apparent reality, based on what appears to us of his speech or action. Yes. We judge him accordingly. As for his ruling with Allah, we do not know about that. Yes.