(18) Their own belly.--Compare the description in Philippians 3:18-19, where the Apostle is also denouncing certain persons who made "a god of their belly." It is not, however, quite clear that the class of persons intended is precisely the same. There the Apostle is condemning Antinomian extravagances which professed to be based on his own teaching; here he would seem to have in view some more radical divergence of doctrine, "contrary to" that which they had learned. Selfish indulgence is unfortunately a common goal, to which many diverse ways of error will be found to lead.

By good words and fair speeches.--The difference, perhaps, is between "insinuating" or "specious" address, and "fine phrases" in a rhetorical sense.

Simple.--Literally, guileless. Those who have no evil intentions themselves, and do not readily suspect others of them.

Verses 18-20. - For they that are such serve not our Lord Jesus Christ, but their own belly (cf. Philippians 3:18, 19). Had St. Paul thought these people sincere though mistaken, he would doubtless have treated them with the tenderness he shows towards the weak brethren. But he regards them as self-interested, and of the flesh; and against such disturbers of the Church's peace he is, here as elsewhere, indignant (el. Galatians 1:7, 8; Galatians 2:4; Galatians 3:1; Galatians 5:11, 12). In speaking of them as serving, or being slaves to, their own belly, it cannot be concluded certainly that he attributed to them habits of sensuality. He may only mean that it is the gratification of the lower part of their nature that they have in view; and there may be allusion to the motive of such persons being the desire of eating and drinking at the cost of the Churches. In 'The Teaching of the Twelve Apostles' (alluded to under Romans 12:6, seq.) the desire to live without working at the cost of the Church is set down as one of the marks of a false apostle or a false prophet. And by good words and fair speeches deceive the hearts of the simple (rather, innocent, or harmless. So the word ἄκακος is translated in Hebrews 7:26. It is different from ἀκέραιος in ver. 19, though the Authorized Version makes no difference). For your obedience is come abroad unto all men. This is apparently adduced as a reason for his exhorting them to beware of those seducers, with a confidence that they will not be seduced by them, ver. 19 being thus dependent on ver. 17. I am glad therefore on your behalf: but yet I would have you wise unto that which is good, but simple (ἀκεραίους) concerning evil. And the God of peace shall bruise Satan under your feet shortly. The grace of our Lord Jesus Christ be with you all. Amen.

16:17-20 How earnest, how endearing are these exhortations! Whatever differs from the sound doctrine of the Scriptures, opens a door to divisions and offences. If truth be forsaken, unity and peace will not last long. Many call Christ, Master and Lord, who are far from serving him. But they serve their carnal, sensual, worldly interests. They corrupt the head by deceiving the heart; perverting the judgments by winding themselves into the affections. We have great need to keep our hearts with all diligence. It has been the common policy of seducers to set upon those who are softened by convictions. A pliable temper is good when under good guidance, otherwise it may be easily led astray. Be so wise as not to be deceived, yet so simple as not to be deceivers. The blessing the apostle expects from God, is victory over Satan. This includes all designs and devices of Satan against souls, to defile, disturb, and destroy them; all his attempts to keep us from the peace of heaven here, and the possession of heaven hereafter. When Satan seems to prevail, and we are ready to give up all as lost, then will the God of peace interpose in our behalf. Hold out therefore, faith and patience, yet a little while. If the grace of Christ be with us, who can prevail against us?For they that are such serve not our Lord Jesus Christ,.... They do not preach him, but themselves; they do not seek the things of Christ, his honour and glory, the spread of his Gospel, and the enlargement of his kingdom and interest; they seek their own things, worldly honour and applause, riches, wealth, and grandeur; they seek to please men, and so are not the servants of Christ: they introduced the observance of meats and drinks in to the kingdom of Christ, which it do not consist of, and neglected the doctrines of righteousness and peace, from whence springs joy in the Holy Ghost, and so in these spiritual things did not serve Christ; and therefore, as they were not acceptable to God, were not to be approved of by Christian men, but to be marked and avoided:

but their own belly; which they made a god of, and devoted themselves to the service of all their views were to gratify and indulge their sensual appetite. The false teachers among the Jews were particularly addicted to this vice: hence the apostle sometimes calls them dogs, Philippians 3:2, on account of their voraciousness, and who, in Isaiah's time, were greedy ones that could never have enough, Isaiah 56:11; and in our Lord's time devoured widows' houses, under a pretence of long prayers for them, Matthew 23:14; and were like the Cretians, evil beasts, and slow bellies, Titus 1:12, unwilling to labour, and lived upon the spoil of others:

and by good words, and fair speeches, deceive the hearts of the simple: they were deceivers; they lay in wait to deceive, made use of the hidden things of dishonesty, walked in craftiness, and handled the word of God deceitfully; and therefore to be marked and avoided: they deceived "the simple", harmless, and innocent, that think no evil, nor are aware of any; who have little understanding of things; persons of weak minds, easy to be imposed upon; very credulous, ready to believe every word, so the simple man does, as Solomon says, Proverbs 14:15; and such false teachers choose to tamper with, and make their attacks upon, being able to gain upon them the most easily, as their father the devil, the old serpent, did, when he first assailed human nature: the "hearts" of these they deceive; they work upon their affections, blind their understandings, impose on their judgments, and corrupt their minds from the simplicity that is in Christ: and this they do "by good words and fair speeches"; either by making use of the words of Scripture, and a show of arguments taken from thence; so Satan cited Scripture in his dispute with our Lord; and so heretics, in all ages, have pretended toil in favour of their principles, by which means they have gained on many to follow their pernicious ways; or by using words and phrases that faithful ministers of Christ use, such as the grace of God, the righteousness of Christ, the Spirit of Christ, but in a different sense; as some among us now frequently make mention of them, when they mean no more by them than the light of nature within them, and the dictates of a natural conscience; or by an elegant style, a set of fine words, a flow of rhetorical expressions, great swelling words of vanity, which such men generally affect, and so work themselves into the admiration of the common people; or by doctrines suited to the carnal minds and reasonings of men, which tickle human nature, and swell it with pride and vanity; as by preaching up the purity and power of it, asserting man's free will, and the strength of it to that which is good; the capacity of man to keep the law, and perform good works; justification by them before God, and acceptance with him, on account of them; atonement for sins committed, by repentance and reformation; that God does not regard trifling things, some sins are venial, and easily passed over; that concupiscence is no sin; God does not rigorously exact duty, he takes the will for the deed, and is merciful unto all, and if but sincere, there is no doubt of heaven; and such men, generally speaking, instead of correcting vice, and reproving men for their sins, connive at them, indulge them in them, soothe and flatter, commend and defend them, whereby they attach them to their persons and interest.