1 John 2:15-17 Do not love the world or anything in the world. If anyone loves the world, the love of the Father is not in him. For everything in the world--the cravings of sinful man, the lust of his eyes and the boasting of what he has and does--comes not from the Father but from the world. The world and its desires pass away, but the man who does the will of God lives forever.
The last reason given by John for not loving the world is that if we love the world, it means we do not truly understand this great gospel of salvation. ‘The world passeth away,’ says John, ‘and the lust thereof: but he that doeth the will of God abideth forever.’ What he means is this: if you still love the world and the things that are in it, then it is clear that you have never understood the principles of sin. Cannot you see that all that belongs to the world is passing away? All these things, says John, are disappearing, they are dying, You may be proud of your personal appearance, but you will soon be old and haggard. You will be dying, and then you will have nothing to boast of, it is all passing. Oh fool, to glory in something that is so transient! Wealth, riches, learning, knowledge, social status and all these things, they are vanishing, they have the seeds of death in them. Christian people, how can we glory in things like that? It means we are blind to our own gospel which starts by telling us that all that is under the wrath of God and will be destroyed. It is all going to perdition and eternal destruction; so those who live for these things, therefore, are utterly inconsistent and show that they have never understood that if they belong to that realm they will be destroyed to all eternity. They must come out of and escape from it, and they should glory in the fact that there is a new life and realm, a new kingdom, and if they belong to this, they will abide forever.
‘So,’ says the Apostle, ‘that is my injunction to you; realize these truths; do the will of God; do not be concerned about your own desires; Do the will of God, and if you do that, you will abide for ever. You will be building up a firm foundation, a building which will be tried and tested as by fire, but because it consists of god and precious metals and not of wood, hay and stubble, it will last and it will stand the test. And when you arrive in glory, your works will follow you and you will rest in eternal joy from your labors.’
Life In Christ: Studies in 1 John, By Martyn Lloyd-Jones, pg. 221-222.