One thing John emphasizes in his first epistle is the reality and gravity of sin. In 1:8 he forcefully labels those who say they have no sin as self-deceived and void of the truth. In 1:10 the claim not to have committed sin is tantamount to calling God a liar, and in 2:1 John clearly implies that Christians will sin (although he writes to help them avoid it). How then do we understand the statement in 3:9 that the one who is begotten of God "does not do sin" (lit.) and in fact "is not able to sin"?
Following are the major interpretative options (excluding the suggestion of some that John simply contradicts himself):
(1) To avoid the difficulty some have narrowed the definition of "sin" to notorious crimes or offences against love (this was the view of both Augustine and Luther).
(2) It has been suggested that what John means is that a Christian cannot sin because what is sin in the life of an unbeliever is not regarded as such by God when committed by a believer. This is contrary to both John and the rest of the NT.
(3) One interpretation draws a distinction between the "old" nature in the Christian and the "new" nature. The "old" nature may continue to sin but the "new" cannot. But how do we isolate a "nature" from the "individual" himself/herself? We may speak of "flesh" and "spirit" in a person, but it is always the person who sins or does not sin, not merely a "nature".
(4) Others say John is speaking about the ideal and not reality. The argument is: Since all anticipate that sinlessness will be characteristic in the age to come, and since John believed that the age to come had come (2:8), he naturally asserted the sinlessness of Christians!
(5) Some say that John, in the heat of controversial circumstances, breaks forth in holy passion and speaks with apparent exaggeration and over-emphasis.
(6) One view stresses 3:6 where it is stated that the one who "abides" in him does not sin. They contend that this "abiding" in Christ is not descriptive of all Christians but is a condition which only some (those "in fellowship") believers fulfill. The degree of a believer's holiness, then, and his ability to sin or not sin are dependent on whether or not he "abides". When one is abiding in Christ he cannot sin. When one does not abide, one does sin. But 3:9 makes it clear why a Christian doesn't practice sin, indeed, is unable to sin, and it has nothing to do with abiding. It is because he/she "is born of God".
(7) Others say that the sin of which John speaks in 3:9 is willful and deliberate sin. The Christian, so they say, cannot commit such deliberate sin in the face of the Lord. Oh, really? What of David?
(8) A few take John quite literally. Hence they believe he is teaching perfectionism. 3:9 proves that sinlessness is attainable in this life. The statements in 1:8,10 and especially 2:1 are describing the immature believer who although not yet sinless may still become such through diligent activity and love.
[I personally find either of the next two options to be the most likely.]
(9) Some argue that the "sin" which a believer does not and cannot commit is the "sin that leads to death" in 1 John 5:16, namely, hatred of believers and denial of Jesus. I address this view in great detail in my discussion of the sin unto death (see “Controversial Issues” on the web site).
(10) The view adopted by most commentators is that the sin a Christian does not and cannot commit is habitual, persistent, unrepentant sin. John is not concerned so much with the momentary, individual acts of sin as he is with the overall characteristic tendencies and inclinations of a person's life. John is looking at the pervasive temper of one's overall experience in life, not at the singular incidents individually. John is not taking a snapshot, but a moving picture. His repeated use of the Greek present tense appears to bear this out. He focuses on the habitual character of the activity in view.
In 3:6 John says that the believer who abides in Christ "sins not" (present tense). Also, the one who "does sin" (present tense) shows that he has neither seen nor known Him. John nowhere denies that a Christian commits acts of sin. He does deny, however, that the Christian sins persistently, habitually as a reflection of the characteristic inclination of his soul.
Note that in 3:9a he says the one begotten of God "does not do sin." "Again," notes Stott, "it is not the isolated act of sin which is envisaged, but the settled habit of it, indicated by the verb poiein, to do or to practice, which is used of 'doing' sin in 3:4a, 3:8 and 3:9, of 'doing' lawlessness in 3:4b, and of 'doing' righteousness in 2:29, 3:7 and 3:10a" (126).
John also says the one begotten of God "is not able to sin". But again notice that "to sin" is not an aorist infinitive but a present infinitive. If the infinitive had been aorist John would be contradicting what he said in 2:1. The present infinitive again indicates that he has in mind the inability of the born-again believer to habitually live in sin as if it were the prevailing temper of his soul.
If the Christian "does not" practice sin, indeed, "cannot" practice sin, wherein lies this "impossibility"? That is to say, how does a believer avoid the life of persistent sin so characteristic of the non-believer? Stott's answer is excellent:
"Wherein lies this 'impossibility'? John's answer is given in two phrases: for his seed remaineth in him and because he is born of God. . . . his seed is accurately rendered in the RSV text 'God's nature', or 'the divine seed' (NEB), and . . . in him refers to the child of God. In this way the two parts of verse 9 become exactly parallel, each part consisting of a statement that the Christian does not or cannot sin, to which is added the reason for such an assertion. The implication will then be this: the new birth involves the acquisition of a new nature through the implanting within us of the very seed or lifegiving power of God. Birth of God is a deep, radical, inward transformation. Moreover, the new nature received at the new birth remains. It exerts a strong internal pressure towards holiness. It is the abiding influence of his seed within everyone who is born of God, which enables John to affirm without fear of contradiction that he cannot go on living in sin. . . . Indeed, if he should thus continue in sin, it would indicate that he has never been born again" (127).
When those born of God do sin, conviction, grief, brokenness, misery, sorrow, discontent, all of which lead to repentance, will occur.