The sign by which they will know that you are my disciples will be that you love one another.
Jesus speaks to the Apostles of his imminent departure. He is leaving to prepare a place for them in Heaven, but, in the meantime, they remain united to him by faith and prayer.
It is then that he enunciates the New Commandment, proclaimed on every page of the Gospel: This is my commandment, that you love one another as I have loved you. Since then we know that "charity is the way to follow God more closely" and to encounter him more readily. The soul understands God better when it lives charity more finely, because God is Love, and it is ennobled more and more to the extent that it grows in this theological virtue.
The way we treat those around us is the mark by which we will be known as His disciples. Our degree of union with Him will be manifested in our understanding of others, in the way we treat them and serve them. "He saith not the raising of the dead, nor any other evident proof, but this, that ye love one another." "Many ask themselves whether they love Christ, and they go about looking for signs by which they can discover and recognize whether they love him: the sign that never deceives is fraternal charity (...). It is also the measure of the state of our interior life, especially of our life of prayer".
I give you a new commandment, that you love one another..... It is a new commandment because its motives are new: the neighbor is one with Christ, the neighbor is the object of a special love of the Father. It is new because the Model is always current, because it establishes new relationships among men. It is new because the way of fulfilling it will be new: as I have loved you; because it is addressed to a new people, because it requires new hearts; because it lays the foundations of a different and hitherto unknown order. It is new because it will always be a novelty for men, accustomed to their selfishness and their routines.
Hablar con Dios