There is a tendency when we talk about the completeness of justification to react against it. I suppose that is partly because the Gospel teaches us what we are: helpless, hopeless, worthless. No one likes to accept charity, and the Gospel is the ultimate hand-out. It really hurts our ego to see that there's not a thing we can do to buy God off.
But there's another objection too: the instinctive knowledge that God doesn't justify us simply so we can keep doing what we did before.
Years ago, I was younger and more foolish than I am now. I was struggling with the question of eternal security: is it true that a sinner who is justified is justified forever? I was speaking to someone who had been a missionary for years, and he told me "When we were in Africa, we didn't teach the people there eternal security, because otherwise they would just go out and sin". Contemplate that for a while. Isn't that terrible? Not only does it undercut a fellow-believer's sense of security, it actually casts aspersion on the goodness of God! It tells the believer that unless there's something in it for Him, God isn't interested in saving them.
Consider the words of KingJaymz: "I don't think we hear this often enough because it is considered 'dangerous' by many". I think this is precisely what is behind the rampant legalism in the Church today: a fear of what someone might do if they were told there is nothing hanging over their heads. I think that's why Lordship Salvation has become so popular: it codifies a cautious theology.
So what does the Scripture offer as the solution? Does it offer both a complete justification and a Christian life free from lawlessness? Well, yes it does:
Now if we have died with Christ, we believe that we shall also live with Him, knowing that Christ, having been raised from the dead, is never to die again; death no longer is master over Him. For the death that He died, He died to sin once for all; but the life that He lives, He lives to God. Even so consider yourselves to be dead to sin, but alive to God in Christ Jesus. Therefore do not let sin reign in your mortal body so that you obey its lusts, and do not go on presenting the members of your body to sin as instruments of unrighteousness; but present yourselves to God as those alive from the dead, and your members as instruments of righteousness to God. For sin shall not be master over you, for you are not under law but under grace. (Romans 6:8--14, NASB).
The Scripture teaches on the one hand a complete justification: those who believe are justified, declared righteous, acquitted from guilt. But it also teaches that those who are justified are dead with Christ, buried with Him, and raised again with Him. We are free from sin because we are dead with Christ. But we bring forth "fruit" because we are raised with Him too.
"Dead to sin" is a wonderful expression. It goes so much further than anything we can come up with. There is no more complete severance than death. The Scripture mentions a few things the believer is "dead to", including sin (Romans 6), the law (Romans 7, Galatians 2), and the world (Galatians 6). One real problem in modern Christianity is, we simply can't accept our place as "dead". As long as we try to be less than fully dead in an area, we'll have trouble in it.
But we're not only dead, we're also raised: this is the Biblical answer to the "what about the fruit?" question. As risen, resurrected people, we are able to bring forth fruit to God. Notice the motivation here: we tend to think in terms of incentive and punishment, but the term "fruit" implies organic growth: we bring forth fruit that reflects what we are. When what we are has changed, so does the fruit. Or, in the language of Romans 6, we are to live as "those that are alive from the dead". Not as those who are out to prove something, but as those that have undergone a fundamental transformation.
If we consider Romans 7 and 8, we see that there is still a problem within: we still carry around what Romans refers to as "the flesh". We're stuck with it until the "redemption of the body" in Romans 8. And it has a tendency to cause us lots of trouble: Galatians 5 and 6 give us a good deal of insight into that battle. So no, not everything a true believer does is good. True believers have this "flesh" too: there will still be problems in our lives.
The fruit we buy in the grocery store here where I live often tastes and feels like styrofoam. Why? Because they try to force it to grow, and pick it before it's ripe, so their urban customers can buy it "in season". Similarly, force-grown fruit in the spiritual world is tasteless and inferior. Are believers to bear fruit? Absolutely! But we need to allow the Lord to do the growing, not us. Consider James' account of Abraham:
Was not Abraham our father justified by works when he offered up Isaac his son on the altar? You see that faith was working with his works, and as a result of the works, faith was perfected; and the Scripture was fulfilled which says, "AND ABRAHAM BELIEVED GOD, AND IT WAS RECKONED TO HIM AS RIGHTEOUSNESS," and he was called the friend of God. (James 2:21--23, NASB)Abraham had real faith, and God reckoned it to him as righteousness. That's Romans 4, right? But did Abraham's faith result in complacency? No, it didn't: it resulted in hiim obeying God. How long did it take? About forty years. God doesn't rush when it comes to growing fruit, neither should we. Abraham was justified by faith, and about forty years later, he proved it in his works.
Did Abraham spend those forty years in doubt, concerned that maybe he wasn't justified at all? Neither should we. We trust God's word that we are justified, and we bear fruit in His timetable.
So while I fully expect every justified sinner to bear fruit, I caution strongly against rushing the process.
Please don't take this as a complete answer. Romans 6--8 takes us through several arguments on how this all works. There are complicated implications of these truths. But if we try and hold back from declaring the complete work of Christ on behalf of the sinner---whether by demanding good works for salvation, or by witholding assurance of salvation until a person's life has achieved some level of morality---we are stepping outside the bounds of Scripture. And, we rob the believer of the calm certainty of God's love, which is the foundation of the Christian life.