2 But, because many such things are done by men who seek other objects, and who love not the brethren; let us come back to the tes timony of conscience. How do we prove that many such things are done by men who love not the brethren? How many in heresies and schisms call themselves martyrs! They seem to themselves to lay down their lives for their brethren. If for the brethren they laid down their lives, they would not separate themselves from the whole brotherhood.
Again, how many there are who for the sake of vainglory bestow much, give much, and seek therein but the praise of men and popular glory, which is full of windiness, and possesses no stability! Seeing, then, there are such, where shall be the proof of brotherly charity? Seeing he wished it to be proved, and has said by way of admonition, “My little children, let us not love only in word and in tongue; but in deed and in truth;” we ask, in what work, in what truth? Can there be a more manifest work than to give to the poor?
Many do this of vainglory, not of love. Can there be a greater work than to die for the brethren? This also, many would fain be thought to do, who do it of vainglory to get a name, not from bowels of love. It remains, that that man loves his brother, who before God, where God alone sees, assures his own heart, and questions his heart whether he does this indeed for love of the brethren; and his witness is that eye which penetrates the heart, where man cannot look. Therefore Paul the Apostle, because he was ready to die for the brethren, and said, “I will myself be spent for your souls,” yet, because God only saw this in his heart, not the mortal men to whom he spoke, he says to them, “But to me it is a very small thing that I should be judged of you or at man's bar.” And the same apostle shows also in a certain place, that these things are oft done of empty vainglory, not upon the solid ground of love: for speaking of the praises of charity he says, “If I distribute all my goods to the poor, and if I deliver up my body to be burned, but have not charity, it profits me nothing.” Is it possible for a man to do this without charity? It is. For they that have divided unity, are persons that have not charity. Seek there, and you shall see many giving much to the poor; shall see others prepared to welcome death, insomuch that where there is no persecutor they cast themselves headlong: these doubtless without charity do this. Let us come back then to conscience, of which the apostle says: “For our glorying is this, the testimony of our conscience.” Let us come back to conscience, of which the same says, “But let each prove his own work, and then he shall have glorying in himself and not in another.” Therefore, let each one of us “prove his own work,” whether it flow forth from the vein of charity, whether it be from charity as the root that his good works sprout forth as branches. “But let each prove his own work, and then he shall have glorying in himself and not in another,” not when another's tongue bears witness to him, but when his own conscience bears it.
Source: Homilies on the First Epistle of John (New Advent)