Albert Barnes Commentary Romans 16:18

"For they that are such serve not our Lord Christ, but their own belly; and by their smooth and fair speech they beguile the hearts of the innocent." — Romans 16:18 (ASV)

Serve not. Obey not. Though they are professedly His, they are not His real friends and followers.

But their own belly. Their own selfish desires; their own private interests; they do this to obtain support. The authors of parties and divisions, in church and state, usually have this in view. It is for the indulgence of some earthly appetite, to obtain office or property, or to gratify the love of dominion.

And by good words. Mild, fair, plausible speeches, with an appearance of great sincerity and regard for the truth. (2 Peter 2:3). Men who cause divisions commonly make great pretensions to a special love of truth and orthodoxy, and put on the appearance of great sincerity, sanctity, and humility.

And fair speeches. Greek, (eulogias) eulogy, praise, flattery. This is another very common art. Flattery is one of the most powerful means of forming parties in the church; and a little special attention, or promise of an office, or commendation for talents or accomplishments, will secure many to the purposes of party, whom no regard for truth or orthodoxy could influence for a moment.

Deceive the hearts of the simple. This means the minds of the unsuspecting, or those who are without guile (twn akakwn). The apostle means to identify those who are simple-hearted, without any disposition to deceive others themselves, and therefore without any suspicion of the designs of others.

He has thus drawn the art of forming parties with a master's hand. First, there are smooth, plausible pretences, feigning a great love for truth. Then, an artful mingling of attentions and flatteries; and all this is practised on the minds of the unsuspecting, drawing their hearts and affections toward themselves. Happy would it have been if this art had been confined to his own times.