At this point in the text we have an abrupt break in the flow of thought. Paul had been giving a series of greetings to the believers living in Rome. Then he suddenly stopped as if he were somehow reminded of something very urgent that he must share with these believers for their own safety and protection. It reminds us of Jude when he gave all diligence to write of the common salvation but then he changed what he intended to do because he was suddenly impelled to exhort the people to earnestly contend for the faith and to beware of false teachers (Jude 3 and following).
In these verses Paul sounds out a final warning and exhortation concerning false teachers in which he spells out two ways in which believers may protect themselves against false teachers. The first way is by SEPARATION (verse 17) and the second way is by PENETRATION (Verse 18).
SEPARATION (Verse 17)
The first way we may protect ourselves against false teachers is by SEPARATION. This verse is structured around two commands. Biblical separation can be realized only as these two commands are obeyed. The first command is a command for identification: MARK THEM! It is impossible to separate from a false teacher if you do not know who he is. He must be identified for what he really is. This command is given to the "brethren" in Rome, not just to the elders in Rome and not just to the leadership of this local assembly. Every believer is to show this kind of discernment. Paul was saying, "Make sure you can spot them and identify them. Constantly be on guard, watching for those who might promote false doctrine (compare the warning Paul gave to the Ephesians elders in Acts 20:29-31).
Paul then gives some help in identifying these false teachers, describing them as those who "cause divisions and offenses (stumbling blocks)." Those who are faithful to the Word of God and "narrow minded" in a good way (the Bible is a very narrow book, compare Matthew 7:13-14), are likely going to be accused of being DIVISIVE. "You separatists are always dividing the body of Christ. Why don’t you be more loving and less dogmatic about what you believe?" Etc. Paul reminds us who the divisive ones really are: those who go contrary to the doctrine which has been handed down. In other words, those who cause divisions are those who refuse to stand obediently and faithfully upon the written Word of God, from Genesis to Revelation. Those who move away from that sure foundation are the ones, from God’s perspective, who are causing division. They should not have budged from the rock solid foundation of truth!
These false teachers cause divisions and offenses contrary to the doctrine (teaching) which the Roman believers had received. This preposition para (contrary) is normally translated "along side of." The error creeps up to the truth and comes along side of it. Error always rides closely to the truth and yet it does not quite match up to the truth. It comes close to it though, and is very subtle. Paul expected the Roman believers to know enough doctrine so that they could discern truth from error and thus be able to mark and identify false teachers. They need to be very skilled at telling the difference between that which is counterfeit and that which is true, even though the false and the true may look very similar in many ways. One of the problems in so many churches today is that the people do not know enough doctrine to be able to recognize a person who is teaching contrary to sound doctrine.
Once the false teacher has been marked and identified, what is next? This brings us to our second command which is a command for severance: AVOID THEM! Literally it means, "turn away from them." Notice that we are to separate not merely from their teachings but from them. Alva McClain said it this way, "Get as far away from them as possible."
Concerning those who teach false doctrine, notice what the New Testament tells us in other places:
Let him be accursed (Gal. 1:8-9).
From such turn away (2 Tim. 3:5).
An heretic, after the first and second admonition, reject (Tit. 3:10).
If there come any unto you, and bring not this doctrine, receive him not . . . (2 John 10).
PENETRATION (Verse 18)
The penetration demanded here in verse 18 is twofold. First, there is penetration into their motives ("For they that are such serve not our Lord Jesus Christ but their own belly") and second, there is penetration into their methods ("and by good words and fair speeches deceive the hearts of the simple").
Penetration into their motives: We must penetrate beyond the mere profession. They professed to serve Christ, but Paul penetrated into their true motive. He denied that they served Christ, but rather he discerned that they served their own belly. This was a very strong way of saying that they were SERVING SELF. The word "belly" (6@484") comes from a word meaning "hollow" and can denote the entire physical cavity (often used in the NT of the womb). In John 7:38 it stands metaphorically for the innermost part of man (Vine). In Philippians 3:18-19 Paul used this term to describe the enemies of Christ: "whose God is their belly." Many today claim to be serving Christ but are really striving for personal gain and fame. They care not about the Name and reputation of Christ. They are serving and pleasing SELF and not God.
Penetration into their methods: They deceive the hearts of the simple (literally "without evil", innocent, those who are unsuspecting). These victims are trustful souls who expect nothing bad. How do these false teachers deceive these unsuspecting ones? They do it with good words (words that sound so good, so plausible) and fair speeches (polished language). False teachers really know how to communicate! It is POISON but it is served on such a beautiful platter! They are very smooth talkers. They have a gift at making error sound so good. We remember the words of the serpent in Genesis 3 which sounded so good to Eve. We need to penetrate and look beyond their flattering and polished speeches and discern the hiss of the serpent. Such people are to be marked and avoided!