But our salvation is assured:
1 John 5:16-19 - "If any one see his brother sinning a sin not unto death, he shall ask, and he shall give him life, for those that do not sin unto death. There is a sin to death: I do not say of that that he should make a request. Every unrighteousness is sin; and there is a sin not to death.
We know that every one begotten of God does not sin, but he that has been begotten of God keeps himself, and the wicked one does not touch him. We know that we are of God, and the whole world lies in the wicked one."
Hi, Keith. I agree with your post up till here. On this passage, it just again strikes me as an inconsistency to have John speaking of praying for a brother in v.16 but then switching out immediately to discussing a non-believer in the next verse. The context seems to continually focus on the nature of the sin rather than on different types of people who commit them, so I would have to go with the common reading that he is discussing the sins of believers in both instances, with the sin of denying the Lord being something that no believer can rightly simply ask God to forgive. It must be repented of or there will be no forgiveness.
As for the phrase "every one begotten of God does not sin," he makes the statement that any brother who sins has an Advocate with the Father in 1 John 2:1, and he then refers to true believers "keeping His word" in 1 John 2:5. I take this in the same sense as when he says, "every one begotten of God does not sin." He's not talking about sinless perfection or never sinning. He's talking about preventing himself from defiantly walking in sin, such as when one willfully hates his brother, which he then refers to specifically in 1 John 2:9-11.