Can punishment for unintentional sins be reconciled with Christians knowing they have eternal life?

Eastern Orthodox understanding:

There is no way to offend God or to please God in any way, because God is immutable. Thus sin is not considered as something that offends or pleases God. Instead it is considered more as a harm or as a mistake which you suffer consequences from.

For example - as a metaphor - if you take medicine that has terrible side effects nobody was aware of and you suffer them not really knowing why, you can compare that to committing a sin unknowingly. So until you discover the cause you will suffer the effects of your "sin". If you stop taking those pills and switch to some different pills that do not give you side effects, that would be the "repentance" = you correct your behavior. It does not necessarily mean that this sin will be held against you. That also doesn't mean that you won't suffer from the poison nonetheless. What may be held against you would be if you knew that you were suffering and you did nothing to fix that or you lied to yourself that all is fine.

If you have accepted Christ as your Savior, I see no reason that God would assume you meant only a certain portion of them. If you truly accepted him, it's not going to affect some sins and not others; He suffered for ignorance too 😉. And I believe that principle remains true in such circumstances; it did not say "you will be unforgivably guilty," or in anyway imply that the Atonement would be void for you. I believe it was merely clarifying that you are not perfect if you have even unknowingly done sins, and that, like all sin, which renders you guilty, you will need the Savior to redeem you from those too.

Analogy: You took a bag, without knowing there was a lot of money in it. Your father, who knew there was money in what you took, got the money back to the victim. The wrongdoing has been taken care of. 😀 I love analogies, doesn't that make it so clear?

However, it is also good to remember that sin is not just bad because God will punish you, but that all sin in and of itself is bad; as the scripture you sited puts it, we are "poisoned by bitterness and bound by iniquity." I want to focus on that "bound by iniquity," part. Have you realized that all things that are sins are addictive? aka enslaving? Nobody says, "Oh, I was accidentally kind and took care of that person." But plenty of people look back on times of being rude and demeaning to others with remorse, meaning that they did something that they themselves didn't want to do. So, the scripture is also just pointing out that you are naturally bound by sin, and I would say that is a good way of knowing if what you're doing is sin; if it is something that you do almost involuntarily.

Back to the analogy: It is, of course, better if in the first place, you could look inside the bag and see that there's money in it, and not take it.

Therefore, it is important that you are not only diligent in avoiding sin, but diligent in your coming to learn and understand sin, the nature of it, and recognize it in all its forms, as He does, so that you can really do the former.

P.S. I know for certain that everything I put is not worded perfectly or phrased right, etc. I would love any suggested edits. 🙂
And I don't just mean grammatical corrections.

Sin is sin, whether it is deliberate, unintentional, or resisted but its temptation turns out to be irresistible, leading to rationalisation and even denial that it was ‘really’ a sin. However, God disciplines his stubborn children, the Psalmist saying such a one is blessed! (Ps. 94:12). Such discipline is not at all the same as ‘losing’ salvation. Christians are told:

“Despise not the chastening of the Lord, nor faint when thou art rebuked of him; For whom the Lord loveth, he chasteneth, and scourgeth every son whom he receiveth, If ye endure chastening, God dealing with you as with sons” Hebrews 12:5-7

That alone should clear up the matter; the very idea that God would not correct his children, but allow some sin, hidden to his child, to only come out on the Day of Judgment, so as to damn that one! What kind of a god would do that?

You give two points as “teachings supported by Scripture”, with lists of Scripture references for both. A problem is with the latter half in point 2, namely, that “sinners who sin unknowingly are ‘poisoned by bitterness and bound by iniquity’ until they repent and pray for forgiveness (Acts 8:20-24”). In the text used as support, that person did not know he was poisoned by bitterness and bound by iniquity until the apostle Peter was given that insight (for Simon’s heart condition was revealed – God reads hearts, not men). Then, upon hearing the command to repent of his wickedness and to pray that the Lord might forgive him, Simon the sorcerer besought Simon Peter to pray for him.

It is possible for a believer to do something sinful while feeling very cheerful and convinced that they had not sinned. This can depend on how much they know about the high calling to holiness in word, deed and thought. Christians should become more sensitive to sin as they progress in their Christian lives. Many will say they learned with dismay how many things they used to do for years as new Christians that now they abhor and have learned to turn from. Yet there is an important point about not repenting and praying for forgiveness which can lead to the development of bitterness, and being bound by sin. This is crucial to the answer being sought, and although I can speak from a personal experience 17 years ago, I will not detail that on a public forum.

A Christian has the indwelling of the Holy Spirit, who convicts of sin. It was this work of the Holy Spirit that first led a person to repent of sin and to place all their faith in Christ for salvation. Once a Christian, they become more sensitive to sin as they desire to be more and more like Jesus. Ideally, they will make steady progress but sometimes it’s a case of one step forward, two back. That’s when the Holy Spirit disturbs, until there is prayerful seeking, repentance, and going forward in faith again. Then the peace of God returns.

But if a Christian turns a blind eye to their sin, dismissing it as slight, or rationalising it away with excuses, that is when bitterness can start to take root in their heart, as it did with me, despite several warnings before eventual discipline. Only after God’s discipline fell did I truly face up to my sin, confessing the truth of Hebrews 12:15.

When quoting 1 John 5:18, as to how Christians can know that they have eternal life (present tense), John links that assurance to having “believed in the name of the Son of God”. This is the key to assurance. If the expression of belief is the same as that of the apostle Peter in Matthew 16:13-17, then it will not be a verbal, formulaic response but an exclamation of faith given by the Father’s revelation to us. That’s how it was with Peter, and Jesus rejoiced that Peter’s new understanding had been given to him by God. None of the other apostles (up to that point) had twigged as to just what it meant to believe in Jesus as the Son of God. That expression of belief in the name of the Son of God gets to the core of understanding just who Jesus really is. That is why so many people who sincerely say they are Christians shrink back from expressing assurance about the promise of salvation: the full reality of just who Jesus is has not yet broken through, as it did with Peter. But when that happens, they will know the power of that transforming grace of God, in Christ, and all their confidence will be in that, and not in themselves, either trying (vainly) to live a sin-free life, or diligently and fearfully seeking to confess every sin, known or (impossibly) unknown to them.

Finally, all who trust only in what Christ did to save them should know even now that all their sin was freely pardoned due to the magnitude of what Christ achieved. But on the Day of Judgment all those who followed mere religious systems or formulas, or who were totally irreligious, will discover they are “the goats”, and all their sin will be punished. Their unsaved state will remain. The Righteous Judge of all the earth will judge justly. Everything hidden will be revealed.

So, in answer to, Can punishment for unintentional sins be reconciled with Christians knowing they have eternal life? - It is only those who are not yet children of God who should fear adverse judgment. As the Bible states,

“The Spirit itself beareth witness with our spirit, that we are children of God: And if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with him, that we may be glorified together.” (Romans 8:16-17)

The reconciliation lies in Christians being disciplined by God, before the Day of Judgment, for he knows all their sin, and because they walk in the light of Christ, they see the sin they need to confess, exactly as 1 John 1:6-9 explains.