God is the Author of Love. So, love starts with Him. If you have love and unselfish concern for one another, everyone will know that we are God's disciples. It is because we are reflecting His love to everyone, too.
Let me give you a new command: Love one another. In the same way I loved you, you love one another. This is how everyone will recognize that you are my disciples—when they see the love you have for each other (v. 34-35). Show your love to everyone so that others will feel His love, too.