James doesn’t mince his words into small bits that can be digested easy; he’s on the prowl here because he finds the sin of presumption as arrogance. Here are the words from James 4:13-17:

Now listen, you who say, “Today or tomorrow we will go to this or that
city, spend a year there, carry on business and make money.” Why,
you do not even know what will happen tomorrow. What is your life? You
are a mist that appears for a little while and then vanishes. Instead, you ought to say, “If it is the Lord’s will, we will live and do this or that.” As it is, you boast and brag. All such boasting is evil. Anyone, then, who knows the good he ought to do and doesn’t do it, sins.

Planning, once again, is not the problem. Planning without marking off our future as in God’s hands, signed off perhaps by making the sign of the cross over our future, is the sin. James calls it boasting and bragging.

And here James trades in wisdom, as we see in Proverbs 19:21: “The human mind may devise many plans, but it is the purpose of the Lord that will be established.”

And James reminds the merchants that anyone who knows something to be good and does not do it, for that person it is sin. Sin is here rooted in conscious knowledge.

Merchants know that the future is in God’s hands, not theirs. Therefore, they ought to be putting all futures into the hands of God and entrusting them to him. Instead of presuming and arrogantly seizing control of the future, they ought to be living a life marked by the cross, the life marked by death to our plans and life to God’s.