Leviticus 21:9 - Matthew Poole's English Annotations on the Holy Bible

And by analogy his son also, and his wife, because the reason of the law here added concerns all. And nothing is more common than to name one kind for the rest of the same nature, as also is done Le 18. She profaneth her father, i.e. exposeth his person and office, and consequently religion, one of whose prime ministers he is, to contempt. She shall be burnt with fire; which was the severest of all the kinds of punishments among the Jews. Whereby God would show, both the greatness of their sins who stand in nearer relation to God than others, and how far God is from allowing sin in those who are nearest to him.