In Halakha (Jewish religious law) a Mamzer (ממזר) is a person born of certain forbidden relationships between two Jews. That is, one who is born from a married woman as a product of adultery or someone born as a product of incest between certain close relatives.
The mamzer status is inherited by children; a child of a mamzer (whether mother or father) is also a mamzer. While the word mamzer is often translated as "bastard", unlike the colloquial usage of bastard, a child born out of wedlock or between people of two different faiths is not a mamzer.
A mamzer and his or her descendants are not allowed to marry a regular (non-mamzer) Jewish spouse. He or she is permitted to marry only another mamzer, a convert to Judaism, or (in the case of a man) a non-Jewish female slave.
According to the Shulkhan Arukh, if there are rumors that a married woman is having an affair, the children are not suspected of being mamzerim since the majority of her relations are still with her husband, unless she is exceptionally adulterous. The woman herself is not believed to turn her children into mamzerim.
According to the opinion of Rabbi Moses Feinstein a product of artificial insemination from a mamzer is not a mamzer; there are, however, those that disagree with him.
In a related ruling, Rabbi Joel Teitelbaum declared that children born to a married woman artificially inseminated with the sperm of a man that is not her husband are mamzerim. There are poskim who dispute this ruling.
The children of a mamzer, whether male or female, are mamzerim; likewise their children are mamzerim forever. There are, however, a few exceptions. The product of a male mamzer and a female Gentile slave is a Gentile slave. This relationship is sanctioned by Halakha, even though it is forbidden for any other Jew to marry a Gentile slave. In historical practice, this was the only method acceptable to Halakha to stop the mamzer status from continuing to the next generation. A convert who wished to marry a mamzer could convert to be a Gentile slave and have many of the laws of a regular Jew. The children of the relationship are slaves, and can be freed. After they are freed they are regular Jews and are permitted to marry other Jews. This law is not currently practiced.
The child of a mamzer and a Gentile woman is a Gentile, who can in theory convert and be a regular Jew. However the relationship between the mamzer and the Gentile is not permitted, as no Jew (and a mamzer is considered a Jew) is permitted to marry a non-Jew. (The case of the Gentile slave is different, because non-Jews who became the slaves of Jews were expected to undergo a partial conversion to Judaism.)
An incestuous relationship between two Gentiles does not produce a mamzer.
The child of a married woman and a Gentile man is not a mamzer. However, the child of a woman who is mamzer is a mamzer regardless of who is the father.
The principal approach in Orthodox Judaism has been to follow strict rules of evidence that typically render it impossible to prove either that a prior marriage ever existed or that a child was born of relations outside that marriage. An example is a contemporary responsum by the well-known Israeli Posek Rabbi Ovadiah Yosef to Rabbi Grubner of Detroit, Michigan, establishing an impossibility to prove mamzer status in a situation where the evidence might appear to be clear-cut. The case involved the daughter of a woman who had been married by a Haredi rabbi to a husband who subsequently converted to Christianity and refused to participate in a Jewish divorce. The mother eventually divorced and remarried civilly and had the daughter years later. The daughter, who had been raised as an Orthodox Jew and attended a Haredi day school, brought up the question of her status herself prior to an impending marriage.
Rabbi Yosef proceeded systematically to disqualify evidence that a prior marriage had ever taken place. The mother's evidence was immediately disqualified as an interested party. The ketubah (Jewish marriage contract/certificate) was never found. The rabbi who performed the marriage was contacted, but Rabbi Yosef wrote that his testimony could not be accepted without the ketubah, and in any event required corroboration by a second witness. Attempts to contact the husband were abandoned after an adversarial conversation with his new, non-Jewish wife. Thus, Rabbi Yosef concluded there was insufficient evidence that a valid prior marriage had ever taken place.
Rabbi Yosef then proceeded to establish the possibility that the former husband might be the daughter's father. The mother testified that her former husband occasionally brought alimony payments and came for visitation in person and hence the two were sometimes at least momentarily alone together. Applying an ancient rule that when a husband and wife are known to be alone together behind a closed door the law presumes sexual intercourse may well have taken place, Rabbi Yosef concluded that it was possible the former husband was the daughter's father and hence Jewish law, which very strongly construes all evidence in favor of birth within marriage, had to presume that he was. Thus, Rabbi Yosef concluded that there was insufficient evidence of either a former marriage or that the new husband was the father, and hence he concluded that no evidence of mamzerut had occurred.
Conservative Rabbi Daniel Nevins, commenting on this case, noted that the box of traditional tools Rabbi Yosef brought to bear for discrediting evidence of mamzer status may be sufficiently robust as to cover virtually all cases of inquiry in the types of situations a congregational rabbi would be likely to experience. Nonetheless, Orthodox authorities hold that while contemporary rabbis have authority to refine procedural rules such as rules of evidence, they do not have the authority to abolish biblically mandated categories or procedures entirely.
The Committee on Jewish Law and Standards (CJLS) of the Rabbinical Assembly of Conservative Judaism has declared that Conservative Rabbis should not inquire into or accept evidence of mamzer status under any circumstances, rendering the category inoperative. In doing so, the CJLS distinguished the Conservative approach to Jewish Law from the Orthodox approach, noting that Conservative Judaism regards Biblical law as only the beginning of a relationship rather than a final word, and that the Conservative movement regards it as its role and responsibility to revise Biblical law from time to time when such law conflicts with evolving concepts of morality.
The CJLS cited cases in the Talmud in which Biblical laws became inoperative, such as when the Sanhedrin stopped meeting at its seat in the Temple in Jerusalem where it was required to meet in order to administer capital punishment, and the abolition of such practices as the rite of Sotah (the ordeal of a suspected adulteress) and the breaking of the heifer's neck in a case of suspected murder as precedents for refusing to administer Biblically mandated procedures on moral grounds. (Other authorities have suggested other reasons, such as the Roman authorities removing the Sanhedrin's ability to administer capital punishment, and the association of certain priestly practices with the existence of a Temple in Jerusalem).
In the State of Israel, religious courts handle matters of marriage, divorce, and personal status in accordance with religious law, so the law of Mamzerut is also Israeli law for Jews, including secular Jews. Because of the severe disabilities of mamzer status with respect to marriage, the Israeli civil authorities have taken the position that the paternity of a child born within a marriage should not be challenged in any court, in order to avoid creating a body of evidence that might be used to declare the child a mamzer or create difficulties for a future marriage.
A recent case, involving a child born eight months and two weeks after a divorce, indicates that the issue raises strong feelings within Israeli society.
The existence of the category of Mamzer, and the disabilities inherent in it, is one of the arguments frequently used by Israeli secularist such as former Education Minister Shulamit Aloni, who call for separation of religion and state and for the institution of civil marriage - since "it is utterly monstrous and unacceptable that the lives of people be ruined and their basic right to create a family with the spouse of their choice be denied due to antiquated, inhuman religious laws which mean absolutely nothing to them".
An extensive report on the issue of Civil Marriage in Israel, written by Prof. Pinhas Shifman and published in July 2001 by ACRI (Association for Civil Rights in Israel), mentions Mamzerim among the categories of Israelis whose basic right to marry a spouse of their choice is denied by the religious monopoly over marriage
Ebalus of Aquitaine, Count of Poitou and Duke of Aquitaine (c. 870 – 935) had the nickname "Manzer" or "Manser".As he is known to have been a bastard and reputed to have had a Jewish mother, this nickname is considered to be derived from "mamzer". A similar explanation is offered also for the same nickname as used by another Prince from Occitania, Arnaud Manzer, Count of Angoulême (born 952-died 988/92) who also was a bastard.