II John 10: "If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed."
Gentle, kind-hearted John now seems stern, hard and uncharitable toward dissenters. Yet one must needs be so because of all the temptation that lurks in the dark.
Outwardly, in word, false doctrine fashions itself so like the truth that without close examination of its substance (whether it’s silver and gold) one cannot discern a difference (even as counterfeits imitate as accurately as possible the impression of genuine metal currency) but the intrinsic worth has been adulterated.
With the true doctrine of Christ, the believers become rich in Him and are saved; with false doctrines the unbelievers are deceived and lost. And because all falsification comes from the wicked one, we may not treat it with indulgence and consideration but must be strict with ourselves, for "A little leaven leaveneth the whole lump . . . (Galatians 4)," and if one safeguards himself as well as he can against a contagious disease, then how much more against the pestilence from hell. But no one can notice a departure from the doctrine of Christ unless through the Holy Ghost he has the apostolic doctrinal example dwelling vibrantly in him.
Two things are required for preservation:
(1) We must be well acquainted with the written word of God, which is the standard of life even as it is of faith, from which we may not depart, and this written word of God is the word of the Holy Ghost (the only weapon of attack) wherewith it is possible to smite the wicked one. For this, we must search the word diligently so that we may know what is written (Matthew 4; Acts 17; John 5), not only as precisionists and scribes but as the taught of God.
(2) For this further is required the Holy Spirit as the only expounder of what is written, so that we may not become confused by false application of the word. Even inconsiderable complaisance is dangerous and destructive. We may accept nothing except what is written.
-Excerpt: Writings of Samuel Froehlich