1 While the disciples thus question, and Jesus their Master replies to them, we also, as it were, are learning along with them, when we either read or listen to the holy Gospel. Accordingly, because the Lord had said, “Yet a little while, and the world sees me no more; but you shall see me,” Judas— not indeed His betrayer, who was surnamed Iscariot, but he whose epistle is read among the canonical Scriptures— asked Him of this very matter: “Lord, how is it that You will manifest Yourself unto us, and not unto the world?” Let us, too, be as it were questioning disciples with them, and listen to our common Master. For Judas the holy, not the impure, the follower, but not the persecutor of the Lord, has inquired the reason why Jesus was to manifest Himself to His own, and not to the world; why it was that yet a little while, and the world should not see Him, but they should see Him.
2. “Jesus answered and said unto him, If a man love me, he will keep my word: and my Father will love him, and we will come unto him, and make our abode with him. He that loves me not, keeps not my sayings.” Here we have set forth the reason why He is to manifest Himself to His own, and not to that other class whom He distinguishes by the name of the world; and such is the reason also why the one loves Him, and the other loves Him not. It is the very reason, whereof it is declared in the sacred psalm, “Judge me, O God, and plead my cause against an unholy nation.” For such as love are chosen, because they love: but those who have not love, though they speak with the tongues of men and angels, have become a sounding brass and a tinkling cymbal; and though they had the gift of prophecy, and knew all mysteries and all knowledge, and had all faith so that they could remove mountains, they are nothing; and though they distributed all their substance, and gave their body to be burnt, it profits them nothing. The saints are distinguished from the world by that love which makes the one-minded to dwell [together] in a house. In this house Father and Son make their abode, and impart that very love to those whom They shall also honor at last with this promised self manifestation; of which the disciple questioned his Master, that not only those who then listened might learn it from His own lips, but we also from his Gospel. For he had made inquiry about the manifestation of Christ, and heard [in reply] about His loving and abiding. There is therefore a kind of inward manifestation of God, which is entirely unknown to the ungodly, who receive no manifestation of God the Father and the Holy Spirit: of the Son, indeed, there might have been such, but only in the flesh; and that, too, neither of the same kind as the other, nor able under any form to remain with them, save only for a little while; and even that, for judgment, not for rejoicing; for punishment, not for reward.
Source: Tractates on the Gospel of John (New Advent)