Today Paul draws a strong contrast between the lives lived by those who are imitating him (v.17), and those not.
He writes that, sadly (…with tears…) there are many who are walking as essentially enemies of the cross (v.18) due to their rampant self-indulgence and the glory taken in their lifestyle choices (v.19). Living what Solomon would call a life under the sun (Ecclesiastes 1-2), they make clear through their conduct they are in and of the world.
But, Paul says, the believer must see themselves as one whose true and ultimate citizenship is in heaven. This is a strong word for the Philippians, who despite being geographically distant from Rome, were actually Roman citizens. As a Roman, Caesar was seen as Saviour, and Lord, and would be much-anticipated and waited-for on official visits. Paul says that as citizens of heaven, Jesus is Lord, Jesus is Saviour, and it is for Him that we wait (v.20). He promises far better than any earthly ruler ever could (v.21), and it is for this reason we are to stand firm in the Lord (4.1).
The contrast is stark, the difference is clear. We can choose to live under the sun and as enemies of the cross of Christ, or, we can choose to view ourselves as citizens of heaven, and act accordingly.
No doubt that your wardrobe, social activities, language, customs, culture, and attitudes all reflect a little of where you are from. The big question for us today, then, is do they also reflect where we are going (v.20), and how we are getting there (v.21)?