As Paul has just written to the Galatians about the works of the flesh and the fruit of the Spirit, he understands that we will not always display the fruit of the Spirit perfectly in our lives. Sometimes we or those around us will give in to the works of the flesh. Paul instructs us in two ways that we should approach a fellow believer who is in sin. First of all, we should approach with a spirit of gentleness. Part of this, of course, would be in accordance with Matthew 18 in approaching our brother or sister alone to discuss their sin. In addition, note that we are not to just approach them for the sake of revealing sin but for the purpose of restoring them.