Worldliness is one of the greatest dangers that beset man's soul. It is no wonder that we find our Lord speaking strongly about it: it is an insidious, specious, plausible enemy; it seems so innocent to pay close attention to our business! It seems so harmless to seek our happiness in this world, so long as we keep clear of open sins! Yet here is a rock on which many make shipwreck to all eternity. They "lay up treasure on earth," and forget to "lay up treasure in heaven." May we all remember this! Where are our hearts? What do we love best? Are our chiefest affections on things in earth, or things in heaven? Life or death depends on the answer we can give to these questions. If our treasure is earthly, our hearts will be earthly also. "Where your treasure is, there will your heart be."
Let us learn from our Lord's caution about worldliness, what need we have to watch and pray against an earthly spirit. What are the vast majority of professing Christians round us doing? "They are laying up treasure on earth:" there can be no mistake about it; their tastes, their ways, their habits, tell a fearful tale. They are not "laying up treasure in heaven." Let us beware that we do not sink into hell by paying excessive attention to lawful things. Open transgression of God's law slays its thousands, but worldliness its tens of thousands.
- J.C. Ryle, Expository Thoughts on Matthew, 56-57.