John 13:35

By this. Followers of great teachers reflect the characteristics of their teachers. Love was one of the principal attributes of Jesus. Jesus’ life had been a practical demonstration of love in action. A manifestation of this same kind of love by the disciples of Jesus would give evidence of their relationship and close association with their Master. It is love rather than profession that marks the Christian.

Have love. Literally, “keep on having love.” Constant, fervent manifestations of love, rather than isolated, fitful outbursts of charitableness, are the evidences of discipleship. Paul defines this type of love in 1 Cor. 13. The word there rendered “charity” is the same as the one here translated “love.”