John has a somewhat curious thing to say in verses 16-17. He says,
If anyone sees his brother commit a sin that does not lead to death, he should pray and God will give him life. I refer to those whose sin does not lead to death. There is a sin that leads to death. I am not saying that he should pray about that. All wrongdoing is sin, and there is a sin that leads to death. (16-17)
It seems to me that John is referring to something that James also talked about. James said,
Is any of you sick…The prayer offered in faith will make the sick person well; the Lord will raise him up. If he has sinned, he will be forgiven. (James 5:14-15)
Most times, illness is not the result of a person’s sin, but is merely the result of living in a fallen world. But James leaves room for the judgment of God as being a reason for a person getting sick. And he says that if you pray for such a person, God will not only heal them, but forgive their sin.
But in this passage, John adds a caveat to James’ words. He says don’t bother praying for people whose sin leads to death. What does he mean by that?
I think we find the answer in verses 18-19.
We know that anyone born of God does not continue to sin; the one who was born of God keeps him safe, and the evil one cannot harm him. We know that we are children of God, and that the whole world is under the control of the evil one. (18-19)
One thing that John warns us of again and again is willful, deliberate sin. Again and again he tells us that a true child of God does not make a practice of sin. In verses 18-19, he says the reason for this is that Jesus himself works in us, and that though the whole world is under the control of Satan, we are not. The world may not be able to resist the temptations Satan throws at them, but through the power of God, we can.
For the brother, then, that makes a constant practice of sin, with no sign or remorse or repentance, they are headed for death.
That can mean one of two things. First, that God will bring physical death upon them for their sin. We see this in more than a few places in scripture (Acts 5:1-10, I Corinthians 5:5, 11:27-30)
The other thing it could mean is that such people were not truly ever saved, and that they are headed for eternal death. They knew the truth, they claimed to believe it, and yet by their lives proved they never belonged to God. And he holds them especially accountable because they know the truth. There is no excuse for their behavior. (Hebrews 10:26-31)
In short, not all sins are alike. All of us sin. And as John said, all wrongdoing is sin. But there is a difference between falling into sin and deliberately plunging ourselves into it.
If you fall into sin and repent, God will forgive you. But if you refuse to repent and turn from your ways, there can be no forgiveness for that, only judgment, either in this life or the next, and possibly both.
But John has better hopes for us. He says,
And we know that Son of God has come and has given us understanding, so that we may know him who is true; and we are in him who is true, in his Son Jesus Christ. He is the true God and eternal life. (20)
In other words, Jesus has come, and has opened our hearts and minds to his truth. Now we know God and are in Jesus Christ. He abides in us and we in him, and because of that, we have life.
And so John concludes,
Little children, keep yourself from idols. (21)
John’s telling us, “You belong to the truth now. You belong to the true God. So don’t deliberately offer yourselves to sin and the things of this world. They are mere counterfeits of all that God wants to offer you. Run from sin. And run to Jesus, offering yourself to the one who truly is Life.”
Who are you offering yourself to?