By this [love] all will know that you are My disciples, if you have love for one another. John 13:35
As parents and grandparents, neighbors and relatives, gather ‘round a newborn, one of the first topics of discussion is usually, “Who does the baby look like?” Sometimes the family resemblances are immediate; sometimes they appear in time—especially likenesses based on personality and temperament.
It’s expected that biological children will manifest likenesses of others in their family tree, whether in appearance or personality. And the same thing is true—or should betrue—when it comes to children of God. When Jesus gave His disciples a new command to love each other, He also gave them a reason: By such love, all the world would know that they were His followers (John 13:34-35). And the same is true for us. The world will know we belong to Christ when we demonstrate His love. Love is the only familial marker Jesus mentioned that would tell the world of His followers’ spiritual heritage.
When we demonstrate Christlike, unconditional love—especially to those who don’t know Jesus personally—we are telling the world to whom we belong. The longer we live with love toward others, the better idea the world will have of who Christ is.
The business of the church is to demonstrate God. Bruce Hurt
John Piper sermon: As I Have Loved You, Love One Another