:salam2:
I see many young hot blooded Muslims brothers or some new practicing brothers use term kafir as often as they like.It also pronounce with arrogance and to make them feel superior than others.Clearly here this brother name suggest he is Muslim.Who are we to call another Muslim kafir? Only Allah knows our heart.Be careful who you call Kafir because only Allah knows who is truly a rejector and who is merely a misguided person. It is not up to us to "sentence" a person to the Hellfire.
About calling other Muslims "kafir," we read the following hadith: It is reported on the authority of Ibn `Umar that the Prophet (may peace and blessings be upon him) said: Any person who calls his brother: O Unbeliever! (then the truth of this label) would return to one of them. If it is true, (then it is) as he asserted, (but if it is not true), then it returns to him (and thus the person who made the accusation is an Unbeliever). [Muslim]
Different topic calling non-believer as kafir: Is it right for Muslims to use term kafir for non-believers front of their face? Because this word use mostly to make them feel bad about themself or use as a worst swear ever.
I also heard if someone is kafir, it's our believe to know him as a kafir something like that.It's a fiqhi topic.Hope some knowledgeable brothers and sisters will shed some light on this topic with reference from Quran and Hadith.