Leviticus 18:8

‘If there is a man who lies with his father’s wife, he has uncovered his father’s nakedness; both of them shall surely be put to death. Their bloodguiltiness is upon them.

“A man shall not take his father’s wife so that he will not uncover his father’s skirt.

‘Cursed is he who lies with his father’s wife because he has uncovered his father’s skirt.’ And all the people shall say, ‘Amen.’

“In you they have uncovered their fathers’ nakedness; in you they have humbled her who was unclean in her menstrual impurity.

but that we write to them that they abstain from things contaminated by idols and from sexual immorality and from what is strangled and from blood.

It is actually reported that there is sexual immorality among you, and sexual immorality of such a kind as does not exist even among the Gentiles, that someone has his father’s wife.