But our citizenship is in heaven. And we eagerly await a Savior from there, the Lord Jesus Christ (Philippians 3:20).
As a native of India, my wife carries in her purse something referred to as a "Green Card". This card officially declares her status as a 'resident alien', meaning though she has all the rights associated with living in this country, ultimately this isn't her 'home'. Though she is legally welcome to stay here for life, the government recognizes her identity and sense of belonging are connected with a foreign country.
Paul is saying something very similar in Philippians 3:20, but with a slight difference. His focus is on the community of believers, not the life of an individual believer. The word citizenship would actually be more literally translated as "colony" or "state". In ancient times it often designated an official colony of foreigners or relocated military veterans. Paul is reminding the believers in Philippi that their home is in heaven, and here on earth they are to be a colony of heavenly citizens.
Our churches, as well as our individuals lives, are supposed to consciously model the cultural values of Heaven--not earth. To redo an old phrase, far too many churches are too earthly-minded to be of any heavenly good. Our time on earth is but a few years, but our time in Heaven lasts forever. Isn't it time we began living that future reality now?