פּירוש אויף ויקרא 21:7

זנה is a woman who had sexual intercourse with an Israelite who is forbidden to her as a husband, for instance, with those whom she may not marry under the penalty of excision, or a Gibeonite or a ממזר (that is, a man born from the union of a couple who are liable to excision for such a union) (cf. Sifra, Emor, Chapter 1 7; Yevamot 61b).

כי קדוש הוא לאלוקיו, every member of the tribe is by definition בעל בעמיו, an especially distinguished personage among his people. If he were to marry someone guilty of or unfortunate enough to belong to the categories mentioned in this verse, the husband would no longer be entitled to the sanctity his birthright had not only entitled him to but had expected him to preserve.

וחללה, a daughter of the category of people of whom the Torah had warned in verse 15 that by marrying them he would desecrate his seed.

חללה — This is a woman born from a marriage which is forbidden to the priesthood alone (Kiddushin 77a), e. g., the daughter of a widow and a high priest, or the daughter of a divorced woman [or one released from levirate marriage by the appropriate ceremony (cf. Deuteronomy 25:9)] and an ordinary priest. So also it denotes a woman who became profaned in respect to the priesthood (who lost the right of marrying a priest) through her having previously entered into a union with one of those priests a marriage with whom comes under the term: "marriages forbidden to the priesthood alone”.