James 4:17 declares, "Anyone, then, who knows the good he ought to do and doesn’t do it, sins." A sin of omission is a sin that is the result of not doing something God’s Word teaches that we should do. It is generally used in contrast with the corresponding phrase “the sin of commission,” or sins that a person actively commits. Paul juxtaposes the two concepts in Romans 7:14-20. He decries his tendency toward both types of sin. He does what he doesn’t want to do and knows is wrong—the sin of commission—and he doesn’t do what he knows he should do and really wants to do—the sin of omission. Here is a picture of the new nature in conflict with the flesh in which it dwells.
In the New Testament, the classic example given by Jesus is the account of the Good Samaritan. After a man had been beaten and left in need of help, the first two men to pass by—a priest and a Levite, both of whom knew better—failed to act. The third man, a Samaritan, stopped to show compassion to the man in need (Luke 10:30-37). Jesus used this example to teach that we are to likewise help those in need. By doing so, he clearly communicated that it is sinful to avoid doing good, just as it is sinful to pursue what is evil.
Jesus further describes the sins of omission in Matthew 25:31-46. The goats, those who are sent away by Christ, are those who saw others hungry and thirsty, but did not provide food and water. They are those who saw others in need of clothing, who were sick or in jail but did nothing to clothe or comfort them. These are all examples of sins of omission. There was no sin committed against these needy people—they were not intentionally starved or deprived of their clothing. But the sin of omission was committed when those who could have provided for them chose not to.
Finally, the apostle Paul provides a summary statement that explains why we should do what is right and refrain from sins of omission: “Let us not become weary in doing good, for at the proper time we will reap a harvest if we do not give up” (Galatians 6:9). When we do the will of our heavenly Father (Matthew 12:50), we avoid sins of omission and live productive, fruitful lives pleasing to God (Romans 12:1-2; John 15:1–11).