Once, I called two muslims (let us call them A and B ) Kaafirs (disbelievers) because A said, "I am not muslim," and B said, "I am not a muslim, I am a Jew." Then I asked him (B), "Really?" Then he said, "No." Or the conversation with B was something similar. I think that they were not very serious. Anyway, later on, I read the hadith that says, "Whoever swears by a religion other than Islam is one of them," or it was something like this. So I sent them the hadith and said that they were not muslims. Now how do I repent? Did I become a Kaafir myself, as there is hadith that says, "Whoever calls a believer a Kaafir, one of them is so," or the hadith says something like this? Please help! I do not want to go to hell!

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.

The statements uttered by these two people are grave and serious, even if they were spoken in jest. The Kuwaiti Fiqh Encyclopedia reads:

"Scholars unanimously agreed that a person who utters the words of Kufr (disbelief) is considered a Kaafir, regardless of whether he meant it, was only joking, was being stubborn, or was truly convinced. Allaah, The Exalted, says (what means): {And if you ask them, they will surely say: We were only conversing and playing. Say: Is it Allaah and His verses and His Messenger that you were mocking? Make no excuse; you have disbelieved after your belief. If We pardon one faction of you - We will punish another faction because they were criminals.} [Quran 9:56-66] The words of Kufr that take their sayer out of the fold of Islam are either explicit, such as saying, 'I disbelieve in Allaah,' or, 'I associate partners with Allaah,' or implicit such as, 'Allaah has a physical body,' or 'ʻEesa (Jesus) is the son of Allaah.' It could also be a rejection or denial of an indisputably established ruling of Islam such as the obligation of the prayer or by declaring a prohibited act such as Zina (illicit intercourse) lawful."

It is incumbent on them, in this case, to sincerely repent to Allaah and proclaim the two testimonies of faith anew, and no expiation is due on them. However, they should strive in carrying out good deeds, guard their tongues, and resolve never to speak such words again. Allaah, The Exalted, says (what means): {But indeed, I am the Perpetual Forgiver of whoever repents and believes and does righteousness and then continues in guidance.} [Quran 20:82]

As for you, dear brother, you should beware of calling a fellow Muslim a Kaafir in the future. You should not do anything of the sort except after consulting reliable scholars. Your statements regarding these two people do not make you a Kaafir; however, you should be more cautious in the future.  

For more benefit, please refer to fataawa 87963 and 8106.

Allaah knows best.