1 Cor 5:1

5:1 a man has his father’s wife. The man’s father may have died, or the woman may have been a stepmother. In any case, the sexual relationship in view is the incestuous union explicitly condemned in Lev. 18:8. Though the Greco-Roman culture of Paul’s day tolerated a wide array of immoral activities, even Gentiles censured this kind of incest.