John is warning not to be deceived about this.  Whoever lives righteously is righteous.  In verse 8 he says whoever continues in sin is of the devil.  Jesus said, ‘you shall know them by their fruits (Matthew 7:20).' You can tell what is in a person’s heart by how they live and what they say.

Now this doesn’t mean that you have to live righteously in order to become righteous.  The meaning here is that whoever lives righteously is (already) righteous.  There’s a big difference.  We can’t live right until we are born again and become righteous by the cleansing of the blood of Jesus Christ.

His point here is not to be deceived into thinking a person who continues to practice sin is righteous.  One who has been made righteous will not continue in sin (And he’s not talking about slipping up and occasionally sinning here either for even those who are truly born again and righteous may do that.  And if we do, then if we confess our sin He’ll forgive us.  He’s talking about those who continue to practice sin regularly).

Don’t be deceived—you’ll know them by their fruit!

Confession:

I will not be deceived.  I know that the righteous will live righteously and the sinner will continue in sin.  One who is truly righteous will not continue in sin.