Author Sam Allberry recently wrote a powerful article on Jesus’ words from John 13:34-35: “A new commandment I give to you, that you love one another; just as I have loved you, you also are to love one another. By this all people will know that you are my disciples, if you have love for one another.”

Here’s an excerpt from Allberry’s article:

What will show the presence of heaven itself among God’s people? What will show that God is alive and well and right here? It’s our love for one another. This isn’t an afterthought, as though what really mattered were other things and our love for one another was the icing on the cake. No, the quality of our relational life is to be an apologetic to the world around us. As Francis Schaeffer once wrote, “Jesus is giving the world permission to judge whether we are true Christian disciples on the basis of whether we love one another.”

So how does this work? Why is our love for one another so determinative of our missional success? Let me suggest two reasons.

1. Gospel love creates safety.

We live in a world full of accusation. There’s an ever-present fear of being canceled. The wrong opinion—or even the right opinion expressed wrongly—can land people in catastrophic trouble: fired from work and shunned by those around them.

The church won’t be an effective communicator of the truth if it isn’t an effective community.

The life of the church is an open challenge to this. Christians are always to be most concerned about our own sin, and not someone else’s. Like Paul, believers can think of themselves as “the foremost” of all sinners (1 Tim. 1:15). This creates a culture where people are less likely to be shocked by the sins of others. Sin will not be excused, but a culture of grace will mean the focus isn’t on the speck in someone else’s eye (Matt. 7:3–5).

Moreover, the gospel encourages a posture whereby we’re able to differ with the way people live or think without pushing them away. Jesus was “the friend of sinners”: able to eat with people while not affirming them and able to disagree with others without rejecting them. These distinctions are all but nonexistent in our culture today.

2. Gospel love is marked by diversity.

This is one of the great themes of Ephesians and is most arrestingly expressed in these words: “Through the church the manifold wisdom of God might now be made known to the rulers and authorities in the heavenly places” (Eph. 3:10).

Paul unpacks how the gospel brought reconciliation across the deepest fault line in society, making Jews and Gentiles alike members of a new humanity. One purpose is to showcase God’s “manifold wisdom” in the heavenlies. The church becomes an surprising demonstration of how God can bring together what’s otherwise intractably divided. The love Jesus calls his people to show one another spans varying ethnic, political, cultural, and economic backgrounds. A world watching as such variety comes together in the name of Christ will find its skepticism crumbling.

Many tasks before the church are urgent and essential—defending the faith’s rationality and goodness against attacks, learning to articulate the gospel in various subcultures, caring for the poor and needy in society, bringing the gospel to unreached groups and regions of the world. But nothing can be more urgent or essential than attending to what Jesus says in John 13:35. Arguments can change minds, but the beauty of Christ’s love shown among us will turn heads like nothing else.