This is also a new command because it comes from the new covenant that Jesus brought in. He had referred to this when he shared the bread and wine with his disciples that evening. Jesus said love is the mark of his disciples and, therefore, the church. It is to be a witness to the world. The world is to know the disciples of Jesus not by their zeal or doctrinal purity or code of living but by the love they have for one another.
Love has to be lived out.
There is always a specific person, here in front of us in a concrete situation. Love is the greatest of gifts. Love is a matter of action. The fruit of the Spirit begins with love. Dwight L. Moody wrote that all the other eight can be put in terms of love.