The kohen, or priest, was historically the chief religious functionary of the Jewish people. He served in the Temple and concerned himself exclusively with the study and practice of the Law, the spiritual development of the Jewish people, and the tenacious preservation of the tradition. His ancestry spans all of Jewish history from the Exodus to this very day. It is also the most distinguished family, having been assigned by Divine election to succeed the first-born in the religious leadership of the Jews. Together with the king and the Prophets, the judge and the scholar, he was in the top ranks of communal leadership. The king provided national stability, the judge social stability, and the kohen religious stability and continuity.

The kohen generally had four functions. The first was ceremonial, the offering of sacrifices and the delivery of G‑d’s blessings to the people (Numbers 6:22-26). He also cared for the Temple and carried the Ark.

His second function was to make decisions. The high kohen, during the time of the First Temple, consulted the Urim and Thummim (the breastplate) in order to obtain a "yes" or "no" answer to questions presenting contradictory possibilities.

The third duty was the ritual treatment of disease and tzaraat (leprosy) resulting from violations of the moral or religious code.

Fourth, the kohen was a judge and a teacher. He participated with the elders in judging (Ezekiel 44:24) and also taught Torah (Deuteronomy 33:10). In the era of the two Temples, these functions were preserved in the expectation that the Sanhedrin would contain kohanim. At the destruction of the Second Temple, this function was taken over by the Sages.

The kohen priests were not similar in function or status to pagan priests. There were no orgiastic elements, no cultic funerary rites, no dramatic pagan symbolizing of the life-and-death cycle. The Torah dramatized this difference by placing certain restrictions on the kohen: He is forbidden any contact with the dead, except for his own immediate family and the abandoned dead; he is not permitted to marry a divorcee. The kohen’s integrity sprang from his purity of birth, belief, and action. His Torah was no esoteric lore of cosmic magic; he dealt with laws and morality and taught them to the community at large.

The kohen had a unique mission among Jews, which is clearly distinguished from that of the navi, the prophet. The prophet, whose spirit can be traced to the shepherd, primarily stressed inwardness. He was an individualist who had sudden visions of G‑d and exhorted his fellow Jews concerning severe matters such as idolatry, adultery, and murder. The kohen was also concerned with inwardness, but he insisted that it be outwardly manifested. His pattern can be traced to the farmer. As the farmer is concerned with rows of seeds, the kohen was concerned with the details of his vestments, the measurements of the Tabernacle, the accurate timing of the sacrifices—with order and design. He was not an individualist living outside the community, but one who stayed with the people even in times of the lowest degradation. Despite their differences, the prophet and the priest were considered brothers, as Moses the Prophet and Aaron the Priest were brothers.

Though the prophet was recognized as the highest religious type, it was understood that Judaism could not survive without the kohen and the detailed laws of tradition. The Halakhah embodied prophetic ideals in physical acts, which were administrated by the kohen.

Since the laws required meticulous concern for tradition, the stability of a hereditary priesthood was indispensable. The purity of the kohen’s heredity has guaranteed the purity of his heritage. New scholars arose in every generation and many visionaries were born during the prophetic era; but only the kohen’s ancestry of service remained intact and unshakable in the flux of history. Perhaps because of this, the Jews are referred to in the Bible as a mamlekhet kohanim ve’goy kadosh, a kingdom of kohanim and a holy people (Exodus 19:6).

The Bible (Leviticus 21:6–8) records the relationship of the kohen and the Israelites. Verse six states that because of their exalted function, "they shall be holy unto their G‑d, and not profane the name of their G‑d, for the offerings of the Lord made by fire, the bread of their G‑d, they do offer; therefore shall they be holy." Verse seven emphasizes the strict requirements for their family purity: "They shall not take a woman that is a harlot (zonah), or profaned (chalalah); neither shall they marry a divorced woman (ge’rushah); for he is holy unto his G‑d." In Verse eight the Israelites are instructed to honor the kohen: "Thou shalt sanctify him therefore; for he offereth the bread of thy G‑d; he shall be holy unto thee; for I the L-rd, who sanctify you, am holy."

While the primary functions of the kohen have been suspended since the destruction of the Temple—the sacrifices, the consultation of Urim and Thummim, the treatment of impurities, and the teaching of Torah—some functions remain. He delivers the priestly blessing in the synagogue on holidays in the Diaspora and daily in Israel; and he officiates as the representative of the Temple in the Redemption of the First-Born at the ceremony thirty days after the birth of the first-born male.

Because of his historic association with the Temple and his hereditary position of religious leadership, he is accorded distinguished honors. He is called first to the Torah (only if there is no kohen does an Israelite receive that honor), and he has the privilege of leading the grace after meals. If he forgoes the honor, the leader must recognize his permission. Just as the kohen has certain honors, he also has certain restrictions. He may have no contact with a corpse or be within seven feet (four cubits) from it, be it in a chapel or a grave in the cemetery, or be under the same roof with a corpse unless there is a permanent partition between them. Even today this restriction is enforced. The main highway from Jerusalem to Jericho was built by the Jordanians over a portion of the Mount of Olives cemetery. Since halakahically the kohen may not use the road, signposts indicate an alternate route for kohanim.

A major set of restrictions concerns marriage. As the sacrifice he offered could have no blemish, the kohen himself could have no blemish. Thus to maintain the purity of his lineage he was kept to stricter marriage standards than his Jewish brothers. In addition to prohibitions that apply for all other Jews, the following partners are specifically prohibited to the kohen.

A kohen may not marry a ge’rusha (divorcee), chalalah (woman of defective kohen status), zonah (woman who previously violated certain sexual prohibitions), giyoret (convert) or chalutzah (a Levirate widow). If he does marry any of them, their children likewise become chalalim. Sons born do not have priestly status, and daughter may not marry kohanim.

The law of the kohen is essentially concerned with the pure status of the sons. The children follow the status of the father in terms of "tribe"—kohen, levi, or Israelite—unlike the determination of Jew or non-Jew, which follows the mother. The son, then, inherits the kohen status and bequeaths it in turn to his son. The offspring of a marriage between an Israelite male and a kohen’s daughter would be an Israelite and not a kohen. The reference in the Bible is to be’nei Aharon, the sons of Aaron. Therefore, a kohen daughter may marry any of those prohibited strictly to the kohen; she is subject solely to the laws that inform all Jewish marriages.

Divorcee (Ge’rushah)

The kohen may not marry a divorcee, regardless of the cause of the divorce, the circumstances, or the duration of the previous marriage. If a Jewish divorce was issued for any reason, even though the couple never lived together as man and wife, she may not be married to the kohen. This is true even if a divorce was not biblically necessary, but was required by the Rabbis to prevent public misconception. The issuance of a divorce always precludes marriage to a kohen. While it is a virtue for an Israelite to remarry the wife he divorced (if she had not married another man in the meantime), the kohen may not even remarry his own wife.

If the kohen marries a divorcee despite the restrictions, he has violated the law and is under constant obligation to terminate the marriage even though it is technically valid. Any offspring of the marriage are chalal, of defective kohen status. If the child is a girl, she is not permitted to marry a kohen; if it is a boy, he is prohibited from functioning as a kohen. The kohen’s wife becomes a chalalah as well. If he married a divorcee who was already pregnant, her child is not a chalal, regardless of who the father was. This is because the child was not conceived in sin (lo ba mi-tipat aveirah).

Levirate Widow (Chalutzah)

The Levirate marriage is commanded by the Torah for widows whose late husband was childless. The husband’s brother is required to marry her in order to perpetuate the family of his late brother. In later years, however, the Rabbis saw this as a negative factor and required the ceremony of chalitzah to terminate the requisite marriage to her brother-in-law.

A rabbinic dictum holds that chalitzah is similar to divorce in regard to a kohen marriage, hence a chalutzah is not permitted to marry a kohen.

If a widow who is a doubtful chalutzah marries a kohen, no defect is ascribed to their children. Because it was a rabbinic decree and she is only technically a doubtful chalutzah, her offspring are considered full-fledged kohanim and no divorce is necessary.

Defective Kohen Status (Chalalah)

Chalalah is defined as a defect resulting solely from a specifically kohen violation. It pertains either to the offspring of a prohibited kohen marriage, or to a woman permitted to marry an Israelite but not a kohen, and who has married the kohen in disregard of the law. Technically, it signifies one who is "profaned" from the priesthood.

If the male offspring of the prohibited kohen marriage (the chalal) marries an Israelite woman, she becomes a chalalah. Thus the chalal male offspring continues to pass on the defective kohen status. The female offspring, when marrying Israelites, terminate the defective status. The children of that marriage may marry kohanim because the children follow the father’s lineage.

The kohen himself cannot have his priesthood removed. If he terminates the prohibited marriage, by death or divorce, he may resume his kohen privileges. There is no such thing as the "defrocking" of a kohen.

Zonah

A zonah is a woman who has had incestuous or adulterous relationships, or has had sexual relations with a non-Jew.

In the Halakhah, a zonah is simply one who enters into a sinful union. It is not like the sinful union of the chalalah which violates the specific kohen legislation, but one which violates the basic moral prohibitions (general illicit relations) that apply to all Jews.

There are two schools of thought as to which illicit unions are included under this term. Maimonides, Rashi, Rashba and others hold that all biblically-prohibited unions render the woman a zonah. These prohibitions include those which violate general negative laws (chayyvei lav) such as marriage to a mamzer; violations of positive laws, such as marriage to a Moabite convert; transgressions of those laws that incur the punishment of death or excision, such as incestuous relations; or the marriage of a kohen to a widow who had been guilty of adultery. (An adulterous wife may marry another Israelite even after compulsory divorce from her husband or his death, but she may not marry a kohen.) Each of these women is considered a zonah. There are exceptions to this rule: Prohibited unions, such as those with an animal, are considered criminal and punishable by death, but they do not brand the participant as zonah in a way that would prevent her marriage to a kohen.

Another school of thought was that of the Tosafists, Raavad, Rosh and Tur. They held that only violations of prohibitions that incur death and excision, such as incest and adultery, brand a woman zonah. But violating general negative or positive commandments does not categorize the woman as zonah, although she is nonetheless prohibited from marrying the kohen. But if she is prohibited to a kohen, what difference does it make if she is technically a zonah or not? The answer is that the child of a zonah may not marry a kohen, while the child of a prohibited but non-zonah marriage may marry a kohen.

The following are additional instances of zonah: (I) A Levirate widow who marries without the necessary chalitzah is considered a zonah, since her marriage was not valid, and she may not marry a kohen. (2) A woman, divorced from her husband, who marries another man who then dies or divorces her, and she subsequently remarries her first husband. She has violated a biblical law but she is not a zonah, and her child is permitted to marry a kohen. (3) A woman who has committed secondary (rabbinically-legislated) incest is not a zonah, and she is biblically permitted to marry a kohen.

Female Convert (Giyoret)

Converts, because they come from diverse cultures, are all classed in the category of statutory zonah. This is no reflection whatsoever upon the integrity of the convert; on the contrary, righteous converts were held in great personal esteem. But the law had to pronounce on converts as a group, because no investigation could prove totally reliable. Also, one must remember that the boundaries of the zonah category were not those of the harlot, but were related to the peculiar kohen requirements.

The codifiers disagree as to whether the classification of giyoret as zonah is biblical or rabbinic. Indeed, according to Raavad, it reflects only the kohen’s concern with the purity of his lineage. Thus a child of parents who were both converts before they married is technically permitted to marry a kohen because horatah ve’ledatah bi-kedushah (she was conceived and born in sanctity as a Jew). But the kohanim took upon themselves an extra stringency and did not permit it. The blemish here is not zonah, as one can become a zonah only as a consequence of a willful act—one is not born a zonah. It was then decided that the kohen should preferably not marry her but, having done so, he need not be compelled to divorce her. Such a marriage is legal and their child is not a chalal.