Leviticus 20:19-21

‘You shall not uncover the nakedness of your mother’s sister nor of your father’s sister, for that would uncover his near of kin. They shall bear their guilt. If a man lies with his uncle’s wife, he has uncovered his uncle’s nakedness. They shall bear their sin; they shall die childless. If a man takes his brother’s wife, it is an unclean thing. He has uncovered his brother’s nakedness. They shall be childless.