“And it is true, and lies not. Even as it has taught you, abide in it. And now, little children, abide in Him; that, when He shall appear, we may have confidence, and not be put to shame by Him at His coming. If you know that He is righteous, know ye that every one that does righteousness is born of Him. Behold, what manner of love the Father has bestowed upon us, that we should be called and should be the sons of God: therefore the world knows us not, because it knew not Him, us also the world knows not.
Beloved, now are we the sons of God, and it is not yet manifested what we shall be. We know that, when He shall appear, we shall be like Him; for we shall see Him as He is. And every man that has this hope in Him purifies himself, even as He is pure. Whosoever commits sin commits also iniquity. Sin is iniquity. And ye know that He was manifested to take away sin; and in Him is no sin. Whosoever abides in Him sins not: whosoever sins has not seen Him, neither known Him. Little children, let no man seduce you. He that does righteousness is righteous, even as He is righteous. He that commits sin is of the devil; for the devil sins from the beginning. For this purpose the Son of God was manifested; that He might destroy the works of the devil.</em>”
Source: Homilies on the First Epistle of John (New Advent)