“Anyone then who knows the good he ought to do and doesn’t do it sins.” James 4:17
A Sunday School teacher who was speaking to her class on the topic of sin asked, “Can anyone tell me what the sin of commission is?”
One girl raised her hand. “I know!” she said. “The sin of commission is when you do what you shouldn’t do.”
“That’s right,” the teacher said. “Now can someone tell me what the sin of omission is?”
A boy in the back of the room was anxiously waving his arm, so she called on him. He said, “The sin of omission? Well, those are the sins that you want to do, but you haven’t gotten around to them yet.”
Well, though that might have seemed logical to that young boy, that is not a very accurate description of sins of omission! If we are honest, most of us know when we are sinning. According to James we are tempted to sin, and rather than flee we entertain the sin, which then gives birth to the actual sin, which then gives birth to death. Pretty simple. Sin is a little like inviting a bad habit into our life. At the beginning it is at its weakest, but because it seems weak, we invite it in, nourish it, give it shelter, and when we decide we want to evict it, it has become too strong. Thus it dwells with us until we strengthen ourselves or we weaken it. Both propositions are difficult.
Sins of commission are probably easier to spot than sins of omission. 
Sins of commission are those things that we do that we should not do. Sins of omission, on the other hand, are those things that we should do, but do not do. The sin of omission is the sin of passiveness. It is inaction when action is called for. It is silence when speech is needed (a quiet friend can be worse than a loud enemy). It is not doing those things that God has called us to do. They are maybe even more dangerous than sins of commission. I would guess that most people who think they are “worse than some, but better than most” don’t take sins of omission in consideration. They concentrate on bad things that they don’t do (murder, stealing, adultery, etc.) rather than those good things they don’t do (prayer, reading the Bible, worshipping, serving, etc.).
We tend to think of the Bible as a “can’t do” book. In reality it is a “can do” book which becomes, when we are believers, a “should do” book. Look at all the should do’s that Jesus gave us in his Word. The virgins who were excluded from the wedding because they should have put oil in their lamps (Matt. 25:3-11); the servant who should have used the talent he was given (Matt. 25:25-28); the rich man who should have helped his neighbor (Luke 16:19-24); and even Christ’s admonition to those who should have fed, clothed, housed, or cared for the needy. (Matt. 25:41-36).
There once was a farmer who was praying for the neighbor who was short of food. His five-year-old daughter asked him after the prayer, “Daddy, why are we asking God to give them food when we have food to give?” This world is full of people with good intentions, but what this world really needs are people of great action. When Christ left this earth He left us with the Great Commission, but unfortunately we are much more apt to fulfill the Great Omission. Misdeeds are sins of commission and missed deeds are sins of omission.
So let’s do all we can do to do all we can do. We live in a world of spiritual couch potatoes. Let’s commit ourselves to those things that are not sinful and omit those things that are and we will someday hear the words, “Well done, my good and faithful servant.”
Enjoy this final poem by Margaret Sangster (not to be confused with Margaret Sanger):
It isn’t the thing you do; it’s the thing you leave undone, which gives you a bit of heartache at the setting of the sun.
The tender word forgotten, the letter you did not write, the flower you might have sent, are your haunting ghosts at night.
The stone you might have lifted out of a brother’s way, the bit of heartsome counsel you were harried too much to say.
The loving touch of the hand, the gentle winsome tone, that you had no time or tho’t for with troubles of your own.
The little acts of kindness so easily out of mind; those chances to be helpful which everyone may find.
No, it’s not the things you do, it’s the thing you leave undone which gives you the bit of heartache at the setting of the sun.
May we always remember, “The smallest deed is greater than the grandest intention.” No deed was every done by only thinking about it. Set out today, to do.