1 John 4:2-3, 6

By this you know the Spirit of God: Every spirit that confesses Jesus as the Christ who has come in the flesh is from God, but every spirit that does not confess Jesus is not from God, and this is the spirit of the antichrist, which you have heard is coming, and now is already in the world.

We are from God; the person who knows God listens to us, but whoever is not from God does not listen to us. By this we know the Spirit of truth and the spirit of deceit.