Leviticus 18:5-9

So you shall keep My statutes and My judgments, which, if a person follows them, then he will live by them; I am the Lord.

‘None of you shall approach any blood relative of his to uncover nakedness; I am the Lord.

You shall not uncover the nakedness of your father, that is, the nakedness of your mother. She is your mother; you are not to uncover her nakedness.

You shall not uncover the nakedness of your father’s wife; it is your father’s nakedness.

As for the nakedness of your sister, either your father’s daughter or your mother’s daughter, whether born in the household or born outside the household, you shall not uncover their nakedness.