I write unto you, little children, because your sins are forgiven through His name. I write unto you, fathers, because you have known Him that is from the beginning. I write unto you, young men, because you have overcome the wicked one. I write unto you, children, because you have known the Father. I write unto you, fathers, because you have known Him that is from the beginning. I write unto you, young men, because you are strong, and the word of God abides in you, and you have overcome the wicked one. Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him. For all that is in the world, is the lust of the flesh, and the lust of the eyes, and the pride of life, which is not of the Father, but is of the world. And the world passes away, and the lust thereof: but he that does the will of God abides for ever (even as God also abides for ever).
Source: Homilies on the First Epistle of John (New Advent)