This article had some great points of clarify on a difficult book of the Bible to understand. 1 John. I would like to reemphasize one of his points.
1 John 3:9 Those who have been born into God’s family do not make a practice of sinning, because God’s life is in them. So they can’t keep on sinning, because they are children of God.
1 John was largely written to refute gnosticism. There is much material to cover in what the gnostics believed but I will try to re-explain it in simpler language.
Essentially the gnostics believed that God was not completely good but also had some evil in Him. Thus they believed that a person who was perfectly obeying God and following the Holy Spirit would have sin in their life. Not because man was evil but because a God who was partially evil lead him to do it. Here John is not saying that a christian cannot sin or won’t sin in the future, rather he is saying that God’s Spirit will never lead a person into sin. If you were able to obey God perfectly and follow him without fault you would never sin.
That’s also why it says
1 John 1:5 This is the message we heard from Jesus and now declare to you: God is light, and there is no darkness in him at all.