Negative commandment · Lo Ta’aseh #158 of 613
For a priest not to marry an immoral woman [zonah]
שלא ייקח כוהן זונה
The verse · Vayikra 21:7
אִשָּׁה זֹנָה וַחֲלָלָה לֹא יִקָּחוּ וְאִשָּׁה גְּרוּשָׁה מֵאִישָׁהּ לֹא יִקָּחוּ כִּי־קָדֹשׁ הוּא לֵאלֹהָיו
“They shall not take a wife that is a harlot, or profaned; neither shall they take a woman put away from her husband: for he is holy to his God.”
The Rambam’s words
For a priest not to marry an immoral woman [zonah], as [Leviticus 21:7] states: "They shall not marry an immoral woman or a chalalah."
שלא ייקח כוהן זונה, שנאמר "אישה זונה וחללה לא ייקחו" (ויקרא כא,ז).
Why · Sefer HaChinuch #266
That a priest not marry a licentious woman (zonah)
“It is from the roots of the commandment [that it is] since the priests were chosen to always perform the service of G-d, may He be blessed.”
Who & when
“And [it] is practiced by priests in every place and at all times.”
Where in the Mishneh Torah
Hilchot Forbidden Intercourse הלכות איסורי ביאה