John Chrysostom
Again there is exhortation, and after exhortation, prayer. Having said, beware of those who introduce divisions and do not listen to them, the Apostle added, “The God of peace will crush Satan under your feet,” and, “The grace of the Lord be with you,” Rom 16:20.
Notice how condescendingly he exhorts. He does this not as a counselor, but as a servant, and even with great respect for them.
The Apostle calls them brothers and beseeches them, saying, “I beseech you, brothers.” Then he warns them, revealing the snares of harmful people.
Since these people did not act openly, the Apostle says, “I beseech you, beware.” That is, carefully investigate, learn, and test.
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Whom precisely should they beware? “Those who cause divisions and scandals, contrary to the doctrine which you learned.” Division undermines the Church more than anything else.
It is the devil’s weapon. By it everything is overthrown.
As long as unity is preserved in the body of the Church, the devil cannot gain access. But from division comes scandal.
From what does division arise? From doctrines contrary to the doctrine of the Apostles. And from where do such doctrines arise? From serving the belly and the other passions.
What then should we do with these harmful people? The Apostle did not say, “Go against them and strike them,” but, “avoid them.”
If they did this from ignorance or error, they ought to be corrected. But since they sin knowingly, withdraw far from them.
In another place the Apostle also says, “Withdraw from every brother who walks disorderly,” 2 Thess 3:6.
Regarding Alexander the coppersmith he gives Timothy the same counsel, saying, “Beware of him yourself also,” 2 Tim 4:15.