“In this are manifested the children of God and the children of the devil: Whoever is not righteous is not from God, and whoever does not love his brother.” Now it is clear what he is saying: “And whoever does not love his brother.” Only love distinguishes God’s children from the devil’s. Let them all sign themselves with the sign of Christ’s cross. Let them all answer, “Amen.” Let them all sing, “Alleluia!” Let them all be baptized. Let them all enter the Church. Let them all build the walls of churches. God’s children are distinguished from the devil’s only by charity. Those who have charity are born of God; those who don’t have it are not born of God. The great proof, the great dividing line! Have whatever you wish: if you don’t have this one thing, it does you no good; have it, and you’ve fulfilled the Law. “For whoever loves another has fulfilled the Law,” the Apostle says; and “Love is the fulfilling of the Law” (Rm 13:8, 10).
I think charity is the pearl which the Gospel says that merchant was seeking, the one who found a pearl and sold all that he had and bought it (Mt 13:46). This, charity, is the pearl of great price without which whatever you possess does you no good, while if you have it alone, it is enough for you. You now see with faith; then you will see with sight. If we love even though we don’t see, how shall we embrace when we do see! How are we to exercise ourselves? In love of our brothers and sisters. You can say to me, “I haven’t seen God”; but can you say to me, “I haven’t seen a human being”? Love your brother or sister. If you love the sister or brother that you see, you will at the same time see God, too; because you will see love itself, and God dwells within. (Augustine on I John, Hom 5, 7; PL 35, 2016)