The Torah in Parashat Emor (Vayikra 21:7) commands that a Kohen is not permitted to marry a divorcee. As the Sefer Ha’hinuch explained in the context of a different prohibition, the Kohanim were chosen to serve G-d in the Bet Ha’mikdash, and must therefore adhere to especially high standards of spirituality. For this reason, the Torah imposed a number of restrictions regarding whom a Kohen may marry, including a prohibition against marrying a woman who had previously been married and was divorced.
Even if a woman had only been betrothed, and was divorced before Nisu’in (the completion of the marriage process), she may not marry a Kohen.
If a woman had performed Halisa, a Kohen is forbidden from marrying her Mi’de’rabbanan (by force of Rabbinic enactment). Halisa is the ceremony which is performed when a man dies without children, and his brother chooses to release the wife from the levirate bond instead of marrying her. The woman then resembles a divorcee, and the Sages therefore forbade her from marrying a Kohen.
In some situations, a woman is a “Safek Gerusha” – questionably divorced. One example is a case of a questionable betrothal, where it is uncertain whether the betrothal is binding, and the woman receives a divorce just in case the betrothal had been valid. Her status vis-à-vis marrying a Kohen is thus uncertain. The famous rule of “Safek De’Orayta Le’humra” establishes that one must act stringently in situations of doubt when a Torah law is at stake. Therefore, the woman in such a case may not marry a Kohen. If she did, then in the times when Bet Din had the authority to enforce Torah law, Bet Din would compel the Kohen to divorce her.
If a woman performed Halisa in a situation where it was questionable whether this was necessary, such that her status vis-à-vis marrying a Kohen is uncertain, then if she marries a Kohen, Bet Din will allow them to remain married. Since the prohibition against a Kohen’s marriage to a “Halusa” (woman who had performed Halisa) is forbidden only “Mi’de’rabbanan,” it is treated more leniently. If the Halisa was clearly unnecessary, but, for whatever reason, it was nevertheless performed, the woman is not considered a “Halusa” and she may marry a Kohen.
The Sefer Ha’hinuch writes that it is possible for a Kohen Gadol to transgress four Biblical prohibitions by marrying a woman – if she is a widow, a divorcee, a Halala (meaning, she had a relationship with a Halal, the product a Kohen’s forbidden marriage), and a Zona (meaning, she had a forbidden relationship). Normally, the Sefer Ha’hinuch explains, once something is prohibited, it cannot be prohibited a second time when it becomes subject to an additional prohibition. However, if the additional prohibition is an “Issur Mosif” – meaning, it is more expansive than the first prohibition – then it indeed takes effect. In this case, it is possible for each additional prohibition to fall under the category of “Issur Mosif.” If a woman is a widow, who is forbidden from marrying a Kohen Gadol, and she then marries and divorces, she now becomes forbidden from marrying also ordinary Kohanim. If later she becomes a Halala, then if she is the daughter of a Kohen, she may no longer eat her father’s Teruma, which had been permissible until that point. If she then marries and commits adultery, becoming a Zona, she is also forbidden for her husband and for the adulterer. In this case, then, each subsequent status adds a new prohibition, and thus they all take effect, such that if a Kohen Gadol marries her, he would be liable for four transgressions.
This prohibition applies to Kohanim in all places and in all times. A Kohen who marries a divorcee and consummates the marriage is liable to Malkut.