What does it mean? ---
Do you not have a serious problem, here, with 1 John 3:9? In fact, with the entire third chapter, after the third verse?
Because that verse, for example, seems to imply that whether you were ever saved from Hell is very much in question.
Doesn’t it??? Doesn’t it say that if you have been saved, you CANNOT commit sin? And do you not commit sin?
And there are dozens of similar verses, throughout the Scriptures. Verses like this caused me to doubt, for years, whether I had ever really been saved. I remember recently reading a statement by Billy Graham that he is not sure he had ever been saved.
If you look through the commentaries, even the best of them, I think you will find that few of them have a good, satisfying answer to this problem. Dr. Morris doesn’t even have an entry on the verse, and many that do should have followed his example. Most often, the answers we get from them are:
1. “It doesn’t mean that a Christian can never sin; it means that a Christian cannot live in sin; it means that he does not sin habitually.” I don’t think that cuts it. Paul testifies that he sinned, what I would say he was describing, “habitually.” He said he was a servant to it, in one verse. Although in parallel passages he certainly said he was not. Furthermore, from the Grk, some experts state that that meaning is not justifiable from the Grk. Furthermore, the purpose of 1 John is to give assurance of salvation; and just how does any troubled reader know whether is sin is “habitual” or not? What kind of “assurance” is that to him?? My own doubts were focused on that problem particularly. We are saved from SIN; whether that sin is “habitual” or not has absolutely nothing to do with it; and the sin we are sanctified from is the same sin we are saved from. No; IMO, you can scratch the “habitual” idea completely as any valid exegesis!
2. “A Christian may sin; but he will be miserable when he does; he cannot “live” in it.” But that clearly isn’t even close to what this verse is saying, or the others like it. It’s not talking at all about how sin affects the person doing it; it’s saying the person CAN’T DO IT AT ALL, if he’s born of God!
Can you sin? Then this verse is a problem for you, that you need a better answer for, than the above are giving you.
3. “Etc.” No, that one doesn’t work, either.
The answer is something completely different from all the above! The real answer will be efficacious (to assurance, the purpose of 1 John) and it will make sense. And also, it will not leave us with a contradiction of 1 John 1:8-10, as all the others do.
I think Dr. Donald Grey Barnhouse gave the precise answer, the true one, the only one, the Scriptural one, in his message on Hebrews 10:25-26:
[in a mocking voice, mimicking an opponent] “But it says here, if we sin willfully after we have received the knowledge of the truth, there remaineth no sacrifice for sins . . .”
“These people, that take one verse that they have no idea what it means, and use it to discredit a whole array of other plain well established Scripture . . .”
. . .
“How many of you have never ‘sinned willfully, after you received knowledge of the Truth?’
[pauses, looks around the congregation]
He went on to elaborate on the Truth of the “two men,” which each and every Christian is, like the Christian author Robert Louis Stevenson’s “Dr. Jekyll and Mr. Hyde.” “Each and every one of you who is saved is composed of two persons: for one of whom it is impossible to sin, and for the other of whom it is impossible to do any righteousness.”
And THAT, I believe is the answer to 1 John 3:9. And the answer to ALL the many similar verses and passages.
There is no other answer possible at all!
The “two men” above are named and described thus in Ephesians 4:22-24.
They are named and described in Colossians 3:9-10.
They are described in the entire passage Romans 7:15-25, which cannot be understood apart from an understanding of these “two men.” Thus, in verse 15, the “I’s” are two people: the “I” that “would not” is the “new man;” the “I” which does it anyway is the “old man.”
In vs 17, the “I” that’s not really the one doing it is the “new man;” the “sin that dwelleth in me” is the “old man.”
In vs 22, does any unsaved person “delight in the Law of God after the inward man?” No unsaved person even HAS “the inward man,” which is the “new man,” the one that is given when a person is “born again.” (“born again” is an unscriptural misnomer; it’s simply being born --- that’s where the “new man” came from, once and for all)
Etc. Study it through!
So, 1 John 3:9 is not talking about the whole composite person; it’s talking about “the new man,” and the “new man” only!
Galatians 5 says that if we “walk in the spirit (the “new man”) we cannot fulfill the lusts of the flesh (the “old man”)”
Romans 8 says that they that are in the flesh (the “old man”) cannot please God.
This only scratches the surface of a beautiful and edifying and comforting study. I leave the rest to you!
One last thing: how do we “walk in the spirit?” Forgive me for deviating into a bit of logic, here:
If, and only if, we are walking in the spirit will we “clean up our act,” according to Galatians 5 above. And the only way to “clean up our act” is also stated in Psalm 119:9,11. “If A=B and B=C, then A=C!” IOW, if the way to clean up our act is to “walk in the spirit” and the way to clean up our act is also to have The Word of God active in our heart (Psa. 119:11), then the way to “walk in the spirit” (in the “new man”) is have the Word of God active in our heart.
The same thing was stated by our Lord in John 8:31-32.
GET INTO THE WORD!! Be ambitious to show yourselves approved unto God, by always diligently cutting straight, through The Word. --- 2 Tmothy 2:15.
“Oh how I love Thy Law! It is my meditation day and night!” That is the man who is walking in the spirit --- who is in “the new man.” And no one else is.
Christ Died to Save You
 Or, 1 John 5:18 --- Whosoever is born of God sinneth not . . .Or, John 8:34 “Whoever commits sin is a slave of sin . . . Or, 1 John 3:10 --- Whosoever doeth not righteousness is not of God . . . Or,
 Or, 1 John 3:10 --- If we say “we have not sinned” we make Him a liar, and the Truth is not in us . . . Or 1 Kings 8:46 --- there is no man which sinneth not . . . Or Romans 7:18 --- I know that in me, that is, in my flesh, there dwelleth no good thing . . . Or,
 John 8:34 ought to put that notion to rest once for all! He says that if you sin, you are a slave of sin (and thus it is “habitual”). So do Romans 7b, Job, and many other passages. “Behold, the Heavens are not pure in His sight; how much more abominable and filthy is man, who drinketh in iniquity like water day after day?”