Leviticus 18:1-3, 6, 9

The LORD said to Moses, “Tell the people of Israel: ‘I am the LORD your God. In the past you lived in Egypt, but you must not do what was done in that country. And you must not do as they do in the land of Canaan, where I am bringing you. Do not follow their customs.

“ ‘You must never have sexual relations with your close relatives. I am the LORD.

“ ‘You must not have sexual relations with your sister, either the daughter of your father or your mother. It doesn’t matter if she was born in your house or somewhere else.