16 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. 17 All wrongdoing is sin, and there is sin that does not lead to death.
Wait! What?! There are sins that can lead to death? Really? Well, of course. In the book of Acts we see that Ananias and Sapphira were instantly judged and killed for the sin they committed against God. I started to do quite a bit of scholarly research on these verses to get it clear in my head what the Apostle John means here. He doesn’t explain what a “sin unto death” is, so we can assume that the people he was writing to already had some understanding of this. I found that scholars were divided on the subject and there was quite a bit of varying commentary on this.
When I get confused by the professionals I look to Scriptures. The best place to look for the answer is in the Bible. In Matthew 12: 31 Jesus said,
“I tell you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven.”
Aha! There’s your unforgivable sin. Don’t blaspheme against the Holy Spirit. Now don’t be scared to death (as I was as a teenager) that you might accidentally commit this sin and damn yourself for all eternity. To blaspheme against the Holy Spirit is the willful rejection of Jesus and attributing His works to Satan. That’s what was happening in Matthew 12 when Jesus warned against it.