Levítico 20:17

17 Se um homem tomar a sua irmã, filha de seu pai ou filha de sua mãe, e vir a nudez dela, e ela vir a dele, torpeza é; portanto, serão eliminados na presença dos filhos do seu povo; descobriu a nudez de sua irmã; levará sobre si a sua iniquidade.

17 And if a man takes his sister, daughter of his father or his mother, and has sex relations with her and she with him, it is an act of shame: they are to be cut off before the children of their people; he has had sex relations with his sister, and his sin will be on him.