There’s an old story about the 20th century violin virtuoso, Fritz Kreisler. It animates an important point.
Setting out from Hamburg, Germany, one day to give a concert in London, violinist Fritz Kreisler had an hour before his boat sailed. He wandered into a music shop, where the proprietor asked if he might look at the violin Kreisler was carrying. He then vanished and returned with two policemen, one of whom told the violinist, “You are under arrest.”
“What for?” asked Kreisler.
“You have Fritz Kreisler’s violin.”
“I am Fritz Kreisler,” protested the musician.
“No you’re not. Come along.”
As Kreisler’s boat was sailing soon, there was no time for prolonged explanations. Kreisler asked for his violin and played a piece he was well known for.
Now are you satisfied? He asked.”
The policemen let the musician go because he had done what only Fritz Kreisler could do.
Disciples need to do what they are known for doing, what only they can do. Jesus said, "by this they will know you are my disciples, if you have love for one another. Of course, the kind of love of which Jesus spoke was the divine agape love that He has for us and that He demonstrated by His life and sacrificial death. This is an unconditional love and one which only a disciple, one who has experienced Jesus love and forgiveness, can manifest. So, do what only a disciple of Christ can do. Love others with the same love that you have received in Christ!
Additional Application: If Jesus isn't the person He claimed to be, then explain how it is He is able to do the things He does!