“Children, it is the last hour: and as you have heard that antichrist shall come, even now are there many antichrists; whereby we know that it is the last hour. They went out from us, but they were not of us: if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us. But you have an unction from the Holy One, and know all things. I write unto you, not because you know not the truth, but because you know it, and that no lie is of the truth. Who is a liar but he that denies that Jesus is the Christ? [He is antichrist, that denies the Father and the Son.] Whosoever denies the Son, the same has neither the Father nor the Son: and he that acknowledges the Son has both the Father and the Son. Let that therefore abide in you, which you have heard from the beginning. If that which you have heard from the beginning shall remain in you, you also shall continue in the Son, and in the Father. And this is the promise that He has promised us, even eternal life. These things have I written unto you concerning them that seduce you; that you may know that you have an unction, and that the unction which you have received of him may abide in you. And you need not that any man teach you; because His unction teaches you of all things.”
1. “Children, it is the last hour.” In this lesson he addresses the children that they may make haste to grow, because “it is the last hour.” Age or stature of the body is not at one's own will. A man does not grow in respect of the flesh when he will, any more than he is born when he will: but where the being born rests with the will, the growth also rests with the will. No man is “born of water and the Spirit,” except he be willing. Consequently if he will, he grows or makes increase: if he will, he decreases. What is it to grow? To go onward by proficiency. What is it to decrease? To go backward by deficiency. Whoso knows that he is born, let him hear that he is an infant; let him eagerly cling to the breasts of his mother, and he grows apace. Now his mother is the Church; and her breasts are the two Testaments of the Divine Scriptures. Hence let him suck the milk of all the things that as signs of spiritual truths were done in time for our eternal salvation, that being nourished and strengthened, he may attain to the eating of solid meat, which is, “In the beginning was the Word, and the Word was with God, and the Word was God.” Our milk is Christ in His humility; our meat, the selfsame Christ equal with the Father. With milk He nourishes you, that He may feed you with bread: for with the heart spiritually to touch Christ is to know that He is equal with the Father.
Source: Homilies on the First Epistle of John (New Advent)