Augustine of Hippo, on 1John 4:2

“By this is the spirit of God known. Every spirit which confesseth that Jesus Christ is come in the flesh, is of God:”

“"How," sayest thou, "do I deny in deeds?" Because the end for which Christ came in the flesh, was, that He might die for us. He died for us, because therein He taught much charity. "Greater charity than this hath no man, that a man lay down his life for his friends." Thou hast not charity, seeing thou for thine own honor dividest unity. Therefore by this understand ye the spirit that is from God. Give the earthen vessels a tap, put them to the proof, whether haply they be cracked and give a dull sound: see whether they ring full and clear, see whether charity be there. Thou takest thyself away from the unity of the whole earth, thou dividest the Church by schisms, thou rendest the Body of Christ. He came in the flesh, to gather in one, thou makest an outcry to scatter abroad.”

Imported from an open dataset — not yet checked against the printed edition.