Leviticus 18:6
"'No man is to approach any close relative to have sexual intercourse with her. I am the Lord.
Leviticus 18:7-19
You must not expose your father's nakedness by having sexual intercourse with your mother. She is your mother; you must not have intercourse with her.
Leviticus 20:11-12
If a man has sexual intercourse with his father's wife, he has exposed his father's nakedness. Both of them must be put to death; their blood guilt is on themselves.
Leviticus 20:17-21
"'If a man has sexual intercourse with his sister, whether the daughter of his father or his mother, so that he sees her nakedness and she sees his nakedness, it is a disgrace. They must be cut off in the sight of the children of their people. He has exposed his sister's nakedness; he will bear his punishment for iniquity.