The Literal Commandment
They shall not take a woman who is profaned by harlotry, nor shall they take a woman divorced from her husband; for he is holy to his God. (Leviticus 21:7)
The priests, the sons of Aaron (verse 1) may not take a woman who has been "profaned by harlotry". The Hebrew phrase translated as "profaned by harlotry" uses a word (tzanah) that implies willful and harlotrous behavior.