“If we claim to be without sin, we deceive ourselves and the truth is not in us. If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.” 1 John 1:8-9
“No one who is born of God will continue to sin, because God’s seed remains in them; they cannot go on sinning, because they have been born of God. This is how we know who the children of God are and who the children of the devil are: Anyone who does not do what is right is not God’s child, nor is anyone who does not love their brother and sister.” 1 John 3:9-10
And the meaning of 1 John 3:9 is not that Christians never sin, if that was true there is no born again Christian at all.
It means one born of God does not live a life of continual sin as the unregenerate do, but when they do sin from time to time, they confess it so God will forgive the sin, per 1 John 1:9.
Here’s some scholarship on that:
Whoever abides in Him does not sin: Since sin is lawlessness, a disregard for God (1Jn 3:4), and since Jesus came to take away our sins (1Jn 3:5), and since in Jesus there is no sin (1Jn 3:5), then to abide in Him means to not sin.
i. It is very important to understand what the Bible means - and when it does not mean - when it says does not sin. According to the verb tense John uses, does not sin means does not live a life style of habitual sin. John has already told us in 1Jn 1:8 If we say we have no sin, we deceive ourselves, and the truth is not in us. In 1Jn 1:8, the grammar indicates John is speaking about occasional acts of sin. The grammar of 1Jn 3:6 indicates that John is speaking of a settled, continued lifestyle of sin. John is not teaching here the possibility of sinless perfection.
ii. “The present tense in the Greek verb implied habit, continuity, unbroken sequence” (Stott); the NIV has the right idea when it translates these verbs with phrases such as keeps on sinning, continues to sin, and he cannot go on sinning.
b. Whoever abides in Him does not sin: John’s message is plain and consistent with the rest of the Scriptures. It tells us that a life style of habitual sin is inconsistent with a life of abiding in Jesus Christ. A true Christian can only be temporarily in a life style of sin.
i. Paul’s teaching in Romans 6 is a great example of this principle. He shows us that when a person comes to Jesus, when their sins are forgiven and God’s grace is extended to them, they are radically changed - the old man is dead, and the new man lives. So it is utterly incompatible for a new creation in Christ to be comfortable in habitual sin; such a place can only be temporary for the Christian.
ii. In some ways, the question is not “do you sin or not?” We each sin. The question is, “How do you react when you sin? Do you give into the pattern of sin, and let it dominate your lifestyle? Or do you humbly confess your sin, and do battle against it with the power Jesus can give?”
iii. This is why it is so grieving to see Christians make excuses for their sin, and not humbly confess them. Unless the sin is dealt with squarely, it will contribute to a pattern of sin that may soon become their lifestyle - perhaps a secret lifestyle, but a lifestyle nonetheless.
iv. What is important is that we never sign a “peace treaty” with sin. We never wink at its presence or excuse it by saying, “Everybody has their own sinful areas, and this is mine. Jesus understands.” This completely goes against everything we are in Jesus, and the work He has done in our life.
c. Whoever sins has neither seen Him nor known Him: To live a lifestyle of habitual sin is to demonstrate that you have not seen Him (in a present sense of the ultimate “seeing Him mentioned in 1Jn 3:2), and that you have not known Him. There are some people so great and so wonderful that seeing them or knowing them will change your life forever. Jesus is that kind of person.