2 John 1: 4 - 9
4 I rejoiced greatly to find some of your children following the truth, just as we have been commanded by the Father.
5 And now I beg you, lady, not as though I were writing you a new commandment, but the one we have had from the beginning, that we love one another.
6 And this is love, that we follow his commandments; this is the commandment, as you have heard from the beginning, that you follow love.
7 For many deceivers have gone out into the world, men who will not acknowledge the coming of Jesus Christ in the flesh; such a one is the deceiver and the antichrist.
8 Look to yourselves, that you may not lose what you have worked for, but may win a full reward.
9 Any one who goes ahead and does not abide in the doctrine of Christ does not have God; he who abides in the doctrine has both the Father and the Son.

EWTN