17 Brethren, be followers together of me, and mark them which walk so as ye have us for an ensample.
18 (For many walk, of whom I have told you often, and now tell you even weeping, that they are the enemies of the cross of Christ:
19 Whose end is destruction, whose god is their belly, and whose glory is in their shame, who mind earthly things.
followers together (v.17) = fellow-imitators (always used in a good sense in the New Testament) — join with Paul in the realization that they haven’t attained perfection — contrasted with those in verses 18-19 who are self-righteous and glory in their own accomplishments.
mark (v.17) — note so as to follow the example set — observe others carefully to see if they walk according to Paul’s gospel
us (v.17) — Paul, Timothy, Epaphroditus
ensample (v.17) — example, mold, pattern, model (singular)
enemies of the cross (v.18) — denied Christ while claiming to have obtained righteousness
end (v.19) — not the end of existence, but the outcome of their course of action
destruction (v.19) — not “loss of being” but “loss of well-being”
god is their belly (v.19) — self-indulgence
glory is in their shame (v.19) — they glory in their licentiousness
mind earthly things (v.19) — a noun, “mincers of earthly things”
Paul is evidently referring to those who profess Christ but consider liberty to be license to indulge in sin.
Verses 18 and 19 are perhaps referring to Epicurean Greeks who taught that satisfying the appetites was mans’ highest goal. Some who had heard, and perhaps professed, the gospel may have been in this camp.