2 John 1:8-10

Be on your guard so that you do not lose all that we have diligently worked for but receive a full reward. Anyone who wanders away and does not remain faithful to the teaching of Christ has no relationship with God. But those who remain in the teaching of Christ have a wonderful relationship with both the Father and the Son. So if anyone comes into your fellowship claiming to be a true believer yet doesn’t bring this teaching, you are not to consider him as a fellow believer, nor should you welcome him into your homes.