Ibn `Umar (May Allah be pleased with them) said: The Messenger of Allah (PBUH) said, "When a person calls his brother (in Islam) a disbeliever, one of them will certainly deserve the title. If the addressee is so as he has asserted, the disbelief of the man is confirmed, but if it is untrue, then it will revert to him.‘’ [Al-Bukhari and Muslim].
Abu Dharr (May Allah be pleased with him) said: I heard the Messenger of Allah (PBUH) saying, "If somebody accuses another of disbelief or calls him the enemy of Allah, such an accusation will revert to him (the accuser) if the accused is innocent.‘’[Al-Bukhari and Muslim].
Bukhari and Muslim agree on the report that once Ali sent some money from Yemen to the Holy Prophet, and the Holy Prophet divided it among four men. At this a man who was there said: “O Messenger of Allah, fear Allah!”
The Holy Prophet said:
“Woe to thee! Who on earth is more obliged to fear God than me!”
Khalid Ibn Walid was present. He said:
“Messenger of Allah, should I not kill him?”
The Holy Prophet said:
“No, perhaps he says his prayers.”
Khalid said:
“Many are they who say their prayers, but do not have in their hearts what they say with their tongues.”
The Holy Prophet said:
“I have not been commanded to open up the hearts of people or to cut open their insides.”
oohhh but wait…Ahmedis are not even muslim. WHY? cuz 
according to article 298-c they r not suppose to call themself muslim …
but i wonder what our beloved Prophet ment when he said this…hhmmm 
[INDENT]“If a man calls his Muslim brother kafir, it applies to one of the two.” (Bukhari)
“Whenever a man accuses another of being a *kafir *or wrong-doer, this accusation will rebound on him if the one accused is not in reality a *kafir *or wrong-doer.” (Bukhari)
“The man who calls another *kafir *or enemy of God, and the latter was not such, this charge will indeed turn back upon the accused.” (Muslim)
“He who curses a believer, it is as if he has killed him. And he who accuses a believer of kufr, it is as if he has killed him.” (Bukhari)
[/INDENT]