One of the most crucial – and potentially divisive – issues facing Israeli society today is (once again) who is a Jew – especially in relation to almost 350,000 émigrés from the former Soviet Union who are now living in our midst as “Jewish” citizens of Israel under the Right of Return. Yes, there were indeed more than a million émigrés from the former Soviet Union who made their home in Israel after perestroika, but some 350,000 of them are Jews only by virtue of their paternal – and not maternal – family lineage. Herein lie the seeds of a social explosion.Traditional Jewish law for the past 2,000 years has maintained that a Jew is to be defined as one who either was born to a Jewish mother or has undergone an acceptable process of conversion to Judaism in accordance with time-honored Jewish law (Shulhan Aruch, Yoreh De’a 268). The Sages of the Talmud insisted that it was the maternal – and not paternal – line of descent that determined the Jewish status of the individual (B.T. Kiddushin 68b, based on Deuteronomy 4:7, and Rashi ad loc). Conventional wisdom would add that after all, the fetus is organically tied to the mother, inextricably bound to her in the womb and totally dependent on her for protection and nutrition; moreover, it is the mother who places her life in jeopardy at every birth (until the last century, the most frequent cause of death in women was childbirth). But having said that, it is certainly clear that the father plays a major role in the child as well, determining the gender and contributing his DNA to the fetal genome.This is apparently why, in our opening quotation in this commentary, the census is according to the father’s tribal family; if mother and father are from different tribes, the son is listed as belonging to his paternal tribe. This is similar to the passing down of the kehuna, or priesthood: The son is a priest-Kohen only if his father belonged to the lineage of priest-Kohanim, no matter what his mother’s tribal lineage may have been.A further investigation will reveal that paternal DNA certainly does make a difference, even though it still requires a formal conversion of circumcision and ritual immersion. Indeed, Rabbi Haim Amsalem, a respected rabbi in Israel who was formerly a high-profile leader of the Shas party, has published a monumental two-volume study titled Zera Yisrael (literally “The Seed of the Male Israelite”), documenting many of the responsa that reflect precisely this view – i.e., that a religious court must do everything possible to formally convert an individual whose paternal lineage is Jewish.Here are some salient examples: • The commentary of the Pnei Moshe (Moses Margolies, 1710-1780) on the Jerusalem Talmud queries whether a child born on Shabbat to a gentile mother and Jewish father may be circumcised that following Shabbat (J.T. Yevamot, Chapter 2, Law 5). • Rabbi Moshe Isserles (the Rama) cites the famed Tosafist known as the Ohr Zarua, who speculated as to whether a son born to a gentile mother and Jewish father is considered to be in the category of one who is at least “rabbinically Jewish,” even though he is not Jewish biblically (Kitzur Darkei Moshe on the Shulhan Aruch, Even Ha’ezer, Section 156).• Rabbi Benzion Uziel, the first Sephardi chief rabbi of Israel, ruled that when a Jewish father brings his young male child from a gentile mother to a religious court for conversion, the court is duty-bound (nizkakin) to convert him, because even though the child is considered to have been born of a gentile mother, he is still under the category of “zera Yisrael,” the seed of a male Israelite (Responsa Piskei Uziel, Contemporary Questions, Section 64).• The famed decisor Rabbi David Zvi Hoffman (1843-1921, Slovakia) ruled that a gentile woman who was married civilly to a Jewish Kohen was nevertheless eligible for conversion and a proper marriage (kedat Moshe v’Yisrael) to the Kohen in order to “save” the Kohen from the more problematic sin of living with a gentile woman, and in order to “save” his seed: “It is preferable that she convert, and then the Israelite seed will not be lost” (Melamed Leho’el, Responsum 8).It is also important to note that within our daily prayers every morning, within the blessings of the Shema right before the daily Amida – in the context of praising the truth of the words of the Shema’s three paragraphs – there seems to be a special reference to the descendants of the paternal lineage, the zera Yisrael: “And these words [or matters of the Shema] live and exist, are believed and held to be sweet, forever and for all worlds, upon [the minds and deeds] of our fathers and of ourselves, upon our children and upon our generations, and upon all the generations of the carriers of the seeds of Israel your servant [zera Yisrael avadecha].” (I am indebted to my respected friend Michael Freund, president of Shavei Israel, who brought this reference to my attention.) Hence, there would seem to be a halachic mandate to welcome the zera Yisrael from the former Soviet Union almost like lost Jewish exiles reuniting with their forebears, and to make their formal conversion as embracing and as “user-friendly” as possible. It is also a wonderful opportunity to teach them the treasure trove of Shabbat and festivals that Communist persecution denied them for more than seven decades.This is a perfect example of why it is so important to open the conversion process to city rabbis in Israel, who would actively pursue returning these lost zera Yisrael to their rightful genetic home within historic Israel, knesset Yisrael. Shabbat shalom The writer is the founder and chancellor of Ohr Torah Stone colleges and graduate programs, currently celebrating their 30th anniversary, and chief rabbi of Efrat. The fifth volume of his acclaimed Torah Lights series of parsha commentary was recently published by Koren Publishers.