'Doctrine' in the Bible

Anyone who runs on ahead and does not remain in the doctrine of Christ [that is, one who is not content with what He taught], does not have God; but the one who continues to remain in the teaching [of Christ does have God], he has both the Father and the Son.

If anyone comes to you and does not bring this teaching [but diminishes or adds to the doctrine of Christ], do not receive or welcome him into your house, and do not give him a greeting or any encouragement;