We tend to think that doing wrong is sin. But James tells us that sin is also not doing right. (These two kinds of sin are sometimes called sins of commission and sins of omission.)
It is a sin to lie; it can also be a sin to know the truth and not tell it. It is a sin to speak evil of someone; it is also a sin to avoid him or her when you know he or she needs your friendship. We should be willing to help as the Holy Spirit guides us.
If God has directed you to do a kind act, to render a service, or to restore a relationship, do it. You will experience a renewed and refreshed vitality to your Christian faith.
James 4:17 Remember, it is sin to know what you ought to do and then not do it.