Some contend a Christian no longer commits any sin (ever) after they are born again. This is a false teaching. We will still sin while we are short of glory here on earth, even after being born again of the Spirit, for we are still in fleshly bodies in this fallen world. Others misconstrue 1 John 3:9 to mean that a born-again Christian never sins. Wayne Jackson writes on this misconception: 
In one of his epistles, the apostle John writes:
“Whosoever is begotten of God does not sin, because his [God’s] seed abides in him: and he cannot [ou dunamai] sin, because he is begotten of God” (1 John 3:9).
The apostle is not suggesting that it is impossible for the child of God to sin (cf. 1 John 1:8-9; 2:1-2); rather, he is stating that when divine truth becomes resident in the heart, one will choose not to yield ourselves to a habitual, unrestrained life of sin. The term “cannot” is used in the sense of a moral imperative.
A Christian’s life is one of continued repentance and continued avoidance of deliberate, willful sin. That we may stumble and fall at times is normal, for we are human; and in that case, the apostle John reassures us that we have a faithful Advocate in Christ:
My little children, I am writing these things to you so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous. – 1 John 2:1
If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness. If we say that we have not sinned, we make Him a liar and His word is not in us. – 1 John 1:9-10
Wayne Jackson further writes on 1 John 2:1-2: 
There are several points in this passage that are worthy of notation. Let us briefly concentrate upon them and the meaning they contain for our lives.
- The phrase “little children” is found nine times in this epistle. It reflects the tender love that the apostle had for his fellow Christians. Would it not be wonderful if more of God’s children would treat one another as “family”? This disposition is possible—even when we disagree. Can we not consider each other as “brothers,” rather than “enemies” (2 Thes 3:15)? This does not mean that we are allowed to ignore error; it does address the attitude we should adopt in dealing with our spiritual kinsmen.
- The text underscores the power of the written word; John hopes that his message will inoculate against sin in his brethren’s lives. There are those who believe that an inward, supernatural operation of the Holy Spirit guards them against wrongdoing. John knows nothing of the “zap” ideology. In fact, if such were the case, one could only conclude that the Holy Spirit is doing a mediocre job—since even Christians cannot live above sin. According to the apostle, the written word is the antidote against evil (Psa. 119:11). And when there is failure, the flaw is with us—not the Spirit of God.
- John acknowledges human weakness; he takes note of the fact that sin will overtake us on occasion (see: 1:8; cf. Rom. 7:15; 1 Cor. 10:12). I shall never forget the conversation that I once had with a Christian brother who, deadly serious, stated that he had finally graduated to the level where he sinned no more! I could only listen in stunned amazement, noting that he had eclipsed even God’s apostle. Perhaps John anticipated such arrogance when he wrote, “If we say that we have [present tense] no sin, we deceive ourselves, and the truth is not in us” (1 Jn. 1:8). When we do yield to sin, if the evil is not remedied in the biblical way, even Christians can be cut off from Heaven’s grace (Gal. 5:4)—contrary to the dogma of Calvin.
- When the child of God does sin, however, he need not feel that his situation is hopeless. If he confesses his wrongdoing (1:9), and attempts to turn from such in repentance (Acts 8:22), his “Advocate” (parakletos – a term meaning, “to call to one’s side”) is available to help him. The idea suggested is a legal one; Jesus is the “counsel for the defense” on our behalf. Based upon his own flawless record (cf. “righteous” v.1b), and his atoning mission (1:7), he is qualified to plead our cause. If we practice “walking in the light” (the grammatical tense implies sustained activity), our case will not be lost!
 Jackson, Wayne. “Why Couldn’t Jesus Perform Miracles in His Hometown?” ChristianCourier.com. Access date: May 15, 2019. https://www.christiancourier.com/articles/983-why-couldnt-jesus-perform-miracles-in-his-hometown
 Jackson, Wayne. “A Message from John.” ChristianCourier.com. Access date: May 16, 2019. https://www.christiancourier.com/articles/698-message-from-john-a