So now I am giving you a new commandment: Love each other. Just as I have loved you, you should love each other. Your love for one another will prove to the world that you are my disciples.” (NLT)
The late Francis Schaeffer wrote that it was observable love amongst Christians that was the mark of a Christian to the outside world. Schaeffer was a great defender of biblical truth and affirmed the importance of having a reasoned-out faith with no surrender to wishy washy thinking. And yet he saw clearly that Jesus was saying that the world has a right to assess whether or not we are Christians by our mutual love, or lack of it.
We may well be Christians and not love one another. But the watching world will know we are Christians by that love. Not so much by our public pronouncements denouncing immorality; not so much by our clever marketing strategies; not so much by the content of our belief. These are not the essential witness.
We love one another not by ignoring our differences but by respecting them and focussing on what unites us. Love is not compatibility or even mere niceness. But it does involve sacrificial caring, respectful disagreement, authentic community. Unless we get these internals working properly, all our strenuous efforts at what we call evangelism are in vain. Loving one another is not just a command from God. It is also the very best witness we can offer to a watching world.