In the context of the Torah’s discussion of laws relevant to the Kohen Gadol in Parashat Emor, it commands, “Ve’lo Yehalel Zar’o Be’amav” – literally, “He may not defile his offspring among his nation” (Vayikra 21:15). The Gemara in Masechet Kiddushin explains that this verse refers to a Kohen Gadol who has a relationship with a widow outside the framework of marriage. The previous verse (21:14) forbids a Kohen Gadol from marrying several kinds of women, including a widow. Now the Torah adds a separate prohibition, which forbids a Kohen Gadol from having a relationship that disqualifies a woman or her offspring from marrying a Kohen. The Sages understood that this refers to cohabiting with a widow out of wedlock, a relationship which is not included in the previous verse, as the previous commands, “Lo Yikah” – that a Kohen Gadol may not marry a widow. This second verse thus adds that a Kohen Gadol may not have a relationship with a widow even out of wedlock. It emerges, then, that if a Kohen Gadol marries a widow and then has relations with her, he is guilty of two transgressions, and thus liable to two sets of Malkut, whereas if he has a relationship with a widow without marrying her, he is guilty only of violating “Ve’lo Yehalel.” (The Gemara notes that if a Kohen Gadol merely betroths a widow, without completing the marriage process, he does not violate the prohibition of “Lo Yikah.”) The Sages inferred that this prohibition applies to other Kohanim, as well, forbidding them from cohabiting with women whom they are forbidden from marrying (a divorcee, a “Halala,” and a “Zona”). If a regular Kohen has a relationship with one of these women out of wedlock, he is in violation of this command. However, he is not liable to Malkut, because Malkut are administered only for violating prohibitions mentioned explicitly by the Torah. This command is introduced specifically in reference to a Kohen Gadol, and the Sages inferred its extension to ordinary Kohanim; since this extension is not explicit, an ordinary Kohen is not liable to Malkut for violating this prohibition. In one sense, this prohibition applies specifically to a Kohen Gadol’s relationship with a widow, and not to relationships with the other types of women whom a Kohen Gadol may not marry (divorcee, “Zona,” and “Halala”). Those women are already disqualified from marrying Kohanim, and thus a Kohen Gadol’s relationship with such a woman does not have the effect of “Hilul” – disqualifying her. This command is relevant only to a Kohen Gadol’s relationship with a widow, whom ordinary Kohanim are permitted to marry, but who becomes disqualified for Kohanim through cohabitation with a Kohen Gadol. However, as the Sefer Ha’hinuch discusses, this limitation applies only in the rare case of “He’ara” – if only the beginning of intercourse occurred, but not full intercourse that could produce a child. If complete intercourse occurred, then even in a case of a divorcee, a “Halala” or a “Zona,” the Kohen Gadol had committed an act which disqualifies the offspring from marrying Kohanim, and this act would thus be included under the prohibition of “Ve’lo Yehalel.” It is only regarding “He’ara” that this prohibition is limited to a Kohen Gadol’s relationship with a widow, because the other forbidden women are already disqualified from marrying Kohanim. But if complete intercourse occurred, then a Kohen Gadol violates this prohibition even if the woman belonged to one of the other categories of forbidden women. The reason for this prohibition, as the Sefer Ha’hinuch explained in reference to earlier commands, is that a Kohen Gadol is to maintain especially strict levels of purity and sanctity. To that end, the Torah forbade him from having a relationship with a widow, whose mind might be on her first husband, thus compromising the sanctity of her union with the Kohen Gadol.