Therefore to him that knoweth to do good and doeth it not, to him it is sin. James 4:17
Most of us can quote this scripture by heart. We hear it in sermons. We memorize it in Sunday School. Some of us even try to live by it. The problem of making this scripture a reality in our lives lies in answering the question "What is the good thing?" Here is where an understanding of the original language can be helpful.
There are two words translated "good" from the Greek New Testament. The first is agathos which means moral goodness which is inherent in the nature of the person. This word is rarely used in connection with mankind. In fact, Jesus says that "there is none good except God." (Matthew 10.18) Later we see this type of Goodness listed as one of the fruit of the spirit which God gives to Spirit-Filled believers. Obviously, this is not something that we have control over except in as much as we accept the gift and let it operate in our lives.
The second word is the word used in this passage. It is Kalos. Kalos is moral goodness made practical. This is where agathos rolls up it's sleeves and gets to work. It has a wide range of meanings including: precious, useful, practical, beautiful, and well-adapted to it's ends.
Thayer describes the word this way, "[Kalos is applied to] things so constituted as to answer the purpose for which that class of things was created." I like that definition. Each of us was created (in a class of our own) for a special purpose. Through prayer and Bible reading and practical Christian service we discover that purpose. With that knowledge comes responsibility. Remember our text. If you know what must be done, and you don't do it, then you are sinning. Besides it's a whole lot easier on you if you walk with God rather than fighting against him. (Hint: He's going to win the fight)
Imagine a tree which decides it doesn't want to be a tree. Instead, it wants to be a race car. How foolish, you say. Yet, how many Christians try to do the same thing. God plans for me to teach a Sunday School class, but I insist that his plan for me is to greet people at the door. Or worse, I decide his plan if for me to do nothing at all. As long as I'm running from his will I am miserable. So, doing what you know you ought to do is not only right, but it's smart as well.
There is another definition of this word that I like. It means to be beautiful or pleasing. I saw a poster some time ago which said, "I practice senseless beauty and random acts of kindness." There is something of that in this scripture. Think about reading the scripture this way: "He that knoweth to do something beautiful or pleasing to others and doeth it not, to him it is sin." Being (spiritually) ugly or unpleasant is sinful. How have you brightened your world with a little beauty recently? Could you have sang a song which you didn't? Could you have written some poetry? Could you have taken some flowers to a friend for no reason whatsoever? Could you have helped decorate the church (like on Saturday mornings)?
Sir Arthur Conan Doyle (hardly a Christian by anyone's measure) had his famous detective Sherlock Holmes say something like, "The greatest evidence of a creator is the rose. The random forces of nature could never account for anything which serves no purpose other than beauty." Perhaps your purpose is to bring beauty into this world and thus provide evidence of a creator. And if you know how to do that and you don't....well maybe you had better re-read James 4.17.