Let the lowly brother boast in his exaltation, and the rich in his humiliation, because like a flower of the grass he will pass away. For the sun rises with its scorching heat and withers the grass; its flower falls, and its beauty perishes. So also will the rich man fade away in the midst of his pursuits. (James 1:9–11, ESV)
James was quite possibly writing to Christians who were forced to flee persecution in Jerusalem and seek asylum in Syria or Northern Palestine. Many would have been struggling to find work and make a new life for themselves but the wealthy were using their money to manipulate and were wallowing in self-indulgence rather than minister to those in need.
As Americans, we are far more afraid of being poor than rich. If given the option, most of us would prefer the bigger house, newer car and money in our pockets that wasn't already committed to bills.
The Bible warns of the dangers of wealth in places like 1 Timothy 6:10 and Luke 18:25. Having money (even lots) is not a sin. Our attitude towards it and what we do with it can be. When it comes to our spiritual lives, James issues a caution for the rich (not his last, either). He reminds us that material wealth, just like life, is transient -- temporary. It will fade. It will not last forever. It's spring now and we wait expectantly for the grass and wildflowers to return to life. But we remember a few months ago as they faded from the scene as winter began to make its entrance. Wealth is only temporary and there is no glory in the temporary and insignificant. There is glory, however, in the eternal. Rich and poor alike, we should all find great satisfaction in a life of humility.
The point of what James is saying is summed up well by Douglas Moo:
To the poor believer, tempted to feel insignificant and powerless because the world judges a person on the basis of money and status, James says: take pride in your exalted status in the spiritual realm as one seated in the heavenlies with Jesus Christ himself. To the rich believer, tempted to think too much of himself because the world holds him in high esteem, James says: take pride not in your money or in your social position—things that are doomed all too soon to fade away forever — but, paradoxically, in your humble status as a person who identifies with one who was “despised and rejected” by the world. The point of the passage is, then, that Christians must always evaluate themselves by spiritual and not material standards(Douglas J. Moo, The Letter of James, The Pillar New Testament commentary (Grand Rapids, Mich.; Leicester, England: Eerdmans; Apollos, 2000), 68-69).
Thus says the Lord: “Let not the wise man boast in his wisdom, let not the mighty man boast in his might, let not the rich man boast in his riches, but let him who boasts boast in this, that he understands and knows me, that I am the Lord who practices steadfast love, justice, and righteousness in the earth. For in these things I delight, declares the Lord.” (Jeremiah 9:23–24, ESV)