What ties us together? What do we talk about when we meet, even after a church service? Mere civilities? The weather? Sports? Our careers and our children? Our aches and pains?
None of these topics should be excluded from the conversation of Christians, of course. In sharing all of life, these things will inevitably come up. But what must tie us together as Christians is this passion for the gospel, this fellowship in the gospel. On the face of it, nothing else is strong enough to hold together the extraordinary diversity of people who constitute many churches: men and women, young and old, blue collar and white, healthy and ill, fit and flabby, different races, different incomes, different levels of education, different personalities. What holds us together? It is the gospel, the good news that in Jesus, God himself has reconciled us to himself. This brings about a precious God-centeredness that we share with other believers.
This means that in our conversations we ought regularly to be sharing in the gospel; that is, delighting in God, sharing with one another what we have been learning from his Word, joining in prayer for the advance of the gospel (not least in the lives of those to whom we have been bearing witness), encouraging one another in obedience and maturing discipleship, bearing one another’s burdens, and growing in self-sacrificial love for one another for Christ’s sake.
In short, we must put the gospel first. And that means we must put the fellowship of the gospel at the center of our relationships with fellow believers.
D.A. Carson, Basics for Believers: An Exposition of Philippians (Kindle edition)