Although this question is frequently asked, many attempts to answer it are based on misconceptions or prejudices rather than pure facts. The simple answer to this question is that a person DOES NOT have to stop being Jewish to believe in Jesus. The reasons for this are as follows.
In first place, being Jewish is much more than being a practicing Jew. According to the American Jewish Congress, more than 50% of American Jews are either non-practicing, secular, humanistic, agnostic or atheist. But the remarkable fact is that those Jewish people are still considered Jews! So if religion does not define one’s “Jewishness,” why should the belief in Jesus change one’s “Jewish status”?
Another aspect of this question depends on who gives the answer. According to religious Jews, if a person chooses to believe in Jesus he has “crossed the line.” In other words, if a person chooses to believe in Jesus, he or she has made a conscious decision to become something other than a Jew.
But if Judaism is not defined by one’s beliefs, why should faith in Jesus automatically result in being cut off from the Jewish people? What can be more Jewish than believing that Jesus is the promised Jewish Messiah, who came to fulfill the Jewish prophecies as foretold in the Jewish Bible?
An erroneous view has also been held by the historical Christian churches from the middle of the third century to the present time. The fallacy is the belief that if a Jewish person wanted to follow Jesus, he or she had to forfeit their Jewishness and become a Gentile for all practical purposes.
The First Council of Nicaea, called by the Roman Emperor Constantine I in 325 AD, resulted in the first uniform Christian doctrine, called the Nicene Creed. The purpose of the council was to resolve the nature of Jesus in relationship to the Father; in particular, whether Jesus was of the same substance as God the Father or merely of similar substance.
But another consequence of the Council of Nicaea – followed by the edicts of the Council of Chalcedon and many others – was distancing the church from its Jewish roots. For instance, the council stated that if a Jew wanted to accept Jesus and be part of the church, he had to abandon the Jewish traditions and practices and even change his Jewish name!
Another result of the council was an agreement to abandon the biblical Hebrew calendar and adopt a calendar based on the vernal equinox. All of these changes began to make it impossible for a Jew to believe in Jesus and retain his or her Jewish identity.
The fact is that neither the rabbis’ nor the church’s decrees can take away someone’s Jewishness. The belief that one must stop being Jewish in order to believe in Jesus is as unsustainable as holding that a Scottish, Italian or Chinese person had to stop being Scottish, Italian or Chinese if they chose to believe in Jesus. There is nothing more biblically Jewish than to believe in the Jesus as the Jewish Messiah as described by the Jewish prophets in the Jewish Bible.