4 Everyone who sins breaks the law; in fact, sin is lawlessness. 5 But you know that he appeared so that he might take away our sins. And in him is no sin. 6 No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him. 7 Dear children, do not let anyone lead you astray. He who does what is right is righteous, just as he is righteous. 8 He who does what is sinful is of the devil, because the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the devil’s work. 9 No one who is born of God will continue to sin, because God’s seed remains in him; he cannot go on sinning, because he has been born of God. 10 This is how we know who the children of God are and who the children of the devil are: Anyone who does not do what is right is not a child of God; nor is anyone who does not love his brother.
Pretty clear? The definition of sin is lawlessness, it says so in verse 4. If you continue substituting that word for sin as you re-read the above passage you get a new understanding of obedience and the importance of knowing/following the law (love God, love your neighbor). For example: verses 5 and 6, Jesus appeared so that he might take away our lawlessness. There is no lawlessness in him. If we live in him we won’t be lawless.
Now verse 6 may make you uncomfortable. It sounds like we should not have sin in our lives at all or else that proves we don’t know Jesus. We all sin – can’t help it. Looking at the original Greek helps to understand though, that what is meant here is that we will not make a habit of sinning. That lets us off the hook for the occasional misstep, but also makes us able to spot people who talk the talk but don’t walk the walk. Verse 9 reiterates the idea of not making sin a habit.