Deuteronomy 13:11

And all Israel shall hear and fear, and shall do no more any such wickedness as this is among you; the severity of the punishment as meted out to the seducer should serve to keep them from indulging in similar attempts and, in so far at least, cause the Law to be observed. So far as the Christians are concerned, it is the will of God that they separate themselves from every open, idolater and sinner who seduces others, by excommunicating him. Here the ties of even the closest relationship must be set aside in the interest of God's honor, 1 Corinthians 5:11.