Everyone who practices sin practices lawlessness as well. In fact, sin is lawlessness. But as you know Christ appeared to do away with sin, and in Him there is no sin. No one who remains in Him keeps on sinning. No one who continues to sin has seen Him or known Him.Paul never abolished the Law. It's still there (and as a Jew he observed it). Christians today don't live under it anymore because we have a new Covenant made directly with God. Those who attempt to live under the Law will be judged and condemned by it.
My children, do not be misled: it is the one who does what is right who is righteous, just as Christ is righteous. The one who practices sin is of the devil, because the devil has been sinning from the very start. This is why the Son of God was revealed, to destroy the works of the devil.
Anyone born of God refuses to practice sin, because the Divine seed abides in him; he cannot go on sinning, because he has been born of God. By this the children of God are distinguished from the children of the devil: Anyone who does not do what is right a child of God, nor is anyone who does not love his brother." 1 John 3:4-10
"So then, whoever breaks one of the least of these commandments, and teaches others to do the same, (which amounts to murder) will be called least in the kingdom of heaven." Mat. 5:19
To understand what Jesus meant by saying will be called "least" see Genesis 3:14