Now I beseech you, brethren,.... The apostle being about to finish his epistle, and recollecting that he had not given this church any instructions about the false teachers, who had been the cause of all their differences and uneasiness, inserts them here; or he purposely put them in this place, amidst his salutations, that they might be taken the more notice of; and very pertinently, since nothing could more express his great affection and tender concern for them; and these instructions he delivers to them, not in an authoritative way, as he might, and sometimes did, but by way of entreaty, beseeching them, and with the kind and loving appellation of brethren, the more to engage them to attend to what he was about to say to them:mark them which cause divisions and offences, contrary to the doctrine which ye have learned.
The men he would have taken notice of were such who divided them in their religious sentiments, introducing heterodox notions, contrary to the doctrine of the Scriptures, of Christ and his apostles, and which they had learned from them; such as justification by the works of the law, the observance of Jewish days, and abstinence from meats, enjoined by the ceremonial law, and that as necessary to salvation; to which some gave heed, and others not, and so were divided; whereas the doctrine of faith is but one, the Gospel is one uniform thing, all of a piece; and those that profess it ought to be perfectly joined together in the same mind, and in the same judgment: hence their minds were alienated from each other, and they began to despise and judge one another, yea, to go into factions and parties, being unwilling to receive and admit each other to communion; and thus by these men they were divided in sentiments, affection, and worship; and which must needs cause offence to the church and the godly members of it, as well as cause many so to be offended, as to stumble and fall from the doctrine of faith, and profession of it, and greatly stagger and distress weak believers, and bring a scandal on religion, and the name and ways of Christ among the world, as nothing does more so than the jars and discords among Christians: wherefore the apostle advises to "mark" such persons, look out for, narrowly watch, strictly observe, and diligently examine them: the metaphor is taken from watchmen, who look out from their watch tower, and observe who are coming, or pass by, and take up suspicious persons, and carefully inquire who they are, and what they are about, and whether friends or foes.