“Go to now, ye that say, To day or to morrow we will go into such a city, and continue there a year, and buy and sell, and get gain: Whereas ye know not what shall be on the morrow. For what is your life? It is even a vapour, that appeareth for a little time, and then vanisheth away. For that ye ought to say, If the Lord will, we shall live, and do this, or that. But now ye rejoice in your boastings: all such rejoicing is evil. Therefore to him that knoweth to do good, and doeth it not, to him it is sin.” (James 4:13–17, KJV)
The key to understanding this passage is, well the context, which is summed up in the rhetorical question, “What is your life?” When you’re fifteen, it seems like being your parents age is SO MANY YEARS away. Try this – turn around three times in a circle. Now you’re older than your parents!
At least that’s how it seems.
Don’t put off anything. Schedule things, but don’t procrastinate.
And never procrastinate about doing good!
4:17. It is likely that chapter 4‘s concluding sentence, Anyone, then, who knows the good he ought to do and doesn’t do it, sins, is related not only to the matter of boasting but also to all the advice given thus far in the epistle. “Then” (lit., “therefore,” oun) supports this contention. James’ readers could not plead ignorance. The letter abounds with exhortations to do good. To fail to comply is clearly sin.
J. Ronald Blue, “James,” in The Bible Knowledge Commentary: An Exposition of the Scriptures, ed. J. F. Walvoord and R. B. Zuck, vol. 2 (Wheaton, IL: Victor Books, 1985), 832.