I have been curious about what happens when a Jew decides that Jesus is the "messiah", or accepts any other religion. Does he/she immediately became Christian or something else, and stop being a Jew? I think it is a confusing topic and I was hoping someone could explain please.

This is an important question . . . and all too relevant for very many Jews today, who either fall prey to the many attempts by Christian missionaries (such as the nefarious “Jews for Jesus”) to ensnare Jewish souls, or those who are, most unfortunately, born into an intermarriage, and are thus presented with a choice as to their religious identity. Most people are accustomed to seeing Judaism, or Christianity, or Islam, or other faith systems as simply a religion; and thus it is relevant only to their spiritual lives.  It is not self-definitional.   Ask a typical neighbor “Who are you?”, and they might respond, “My profession is a plumber, my nationality is American, my race is Anglo-Saxon, and my religion is Christian”.   That may accurately reflect the position of the said Christian person.   What I am getting at is that Judaism, unlike other faith systems, is not only a religion, but also a race, or in fact a nation.   We are Am Yisrael – the Nation of Israel.   We are Jews whether we are fully practicing religious Jews, whether we are Orthodox, Conservative, Reform, or Reconstructionist Jews; whether we practice Christianity, Hare Krishna, or even if we profess no religion at all – we are still just as Jewish as the most devoutly religious Orthodox Jew.  Even one who publicly renounces their Jewish faith and turns their back on everything the Torah teaches, remains a Jew.   “Even a deeply sinful Jew, remains a Jew” (Talmud Eruvin 19a).  There is no escaping one’s Jewish identity. Implicit in the Talmudic statement, however, is that though the person who has rejected Judaism remains a Jew, they are considered a sinful Jew, who will ultimately have to answer before the Almighty for their choices.   A Jew who engages in such heretical behavior would be referred to in Halacha as a “Yisrael Mumar”, roughly translated as a Renegade Jew.   The Rabbis of the Talmud ruled that we would not count such a person to a minyan, and in other significant ways we deny them the privileges of Jewish identity.   You might have even heard of a time where the family would sit Shiva for a family member who “converted” to another religion.   But that does not mean that the person is, in fact, no longer Jewish.  Rather, they are no subject to strong legal and public sanction for their actions, as a disincentive to others to follow in their footsteps. In summary, even though accepting another religion is a very serious sin, the person remains Jewish, and is of course welcome back to Jewish practice with open arms.  One only hopes that the person does not intermarry and/or totally assimilate, for then they or their progeny will be totally lost to the Jewish people.

Part of the confusion you have is because unlike a Christian, Muslim or Buddhist – a Jew can mean both the ethnic identity of a person or/and his or her religion. A Jew is part of the Jewish people whether or not he/she is observant and regardless to the level of observance.

 

There have always been Jews who for various reasons have chosen (or forced) to practice a different religion they are still considered according to Jewish law as Jews. The Talmud gives them the status of “sinful Jews”, also referred to as “Mumar” (renegades).

 

Jewish law, halakha, differentiates between five categories of apostates, depending on the form of apostasy and the motivation behind it, from the least severe:

The first three levels of being a “meshumad” or “mumar” do not affect a person’s status within the Jewish people. Such a person continues to be Jewish, even though there might be some restrictions, e.g. someone who violates publicly Shabbat cannot serve as a witness.  The principle is that someone who has turned his or her back on certain mitzvot cannot serve as an agent to fulfil them even should he/she chose to do so. But this doesn’t mean that Halakha considers such a person as a gentile.

 

The status of someone who converted to another religion is more complicated. It depends on the circumstances that led to the conversion (e.g. was the person “trapped” by a skilful recruiter to “Jews for Jesus”), which religion was embraced, the level of immersion and identification with the new religion, the level of rejection of one’s Jewish identity, etc. Now, what happens if such a person at one point decides to re-embrace Judaism? Would he or she need to convert “back” to Judaism in order to annul the previous conversion?  It really depends on the specific case and the circumstances. But there are at least some opinions who would require of somebody who would fall in the “apostate” category four or five to renounce his/her apostasy in front of three witnesses and to immerse in a ritual bath (see: Shulchan Aruch Yoreh Deah 268:12, Rema: “A Jewish apostate who performs Teshuvah (repents) does not need to immerse in a mikvah (in order to return to his former status, on a Torah level); on a rabbinic level he has to immerse and accept upon himself the mizvot in front of three people.”)

 

But whatever the circumstances: the door will always remain open for someone to return. 

While Judaism has long focused more on “deed than creed,” i.e. actions and lifestyle over any religious tenets or dogmatic beliefs, one of the fundamental differences in Jewish and Christian beliefs regard the concept of the messiah. The word “messiah” comes from the Hebrew word mashiach, meaning the “anointed one, who is generally regarded as the one who will bring about a messianic age of peace on earth for all of God’s creatures. For Christians, Jesus of Nazareth is “Christ,” a Greek translation of mashiach, or “messiah.” As Jesus has already come once to earth, the belief of Christians regarding the messiah is one of hoping for Jesus to return to earth. This where the term and subsequent expressions regarding “the second coming” come from. In Jewish belief, the messiah has not yet come, and so we are waiting and hoping for him/her to visit us the one and only time it would be necessary.

 

While many Jews proclaim themselves atheists or agnostics, and many others hope more for a “messianic age” rather than the coming of a singular messiah, this is an area of very stark contrast in traditional belief between Judaism and Christianity. As such, if one has accepted Jesus as a personal savior and messiah, that person has formally parted ways with Judaism and is now a Christian.

 

In the eyes of the Sages of the Talmud, it is much harder to become a Jew if one wasn’t than it is to come back to Judaism. That is to say that Jewish practice creates many more levels and figurative hoops to jump through in order to convert to Judaism than it does barriers to return. If one forsakes Judaism for another faith, but later decides to “return” to Judaism, that person does not need to undergo a formal conversion process. But for as long as the person has accepted Jesus or any deity other than the Eternal as their God, that person would not be considered Jewish.