What does Romans 6:23 mean in comparision to 1 John 5:17?
I can see how someone might see a possible contradiction between Romans 6:23 (The wages of sin is death) and 1 John 5:17 (there is a sin which does not lead to death). However, if you read Romans 6:23 completely and look at the context of both passages, there definitely is no contradiction. The complete Romans 6:23 says, “The wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.” In other words, if we sin, we are liable to “death,” The death that is being discussed here is also called the second death (Revelation 20:14), which is to be sent to hell. Apart from faith in the blood of Jesus, repentance and baptism (Romans 6:4-10), even one sin is sufficient to separate us from God and to make us liable to hell. The story of Adam and Eve illustrates this. Having given this rather bad news, Paul also tells us in Romans 6:23 (and throughout Romans 6 for that matter) that if we become Christians, we have salvation, which includes the forgiveness of our sins (also in 1 John 1:5-7).
This brings me to 1 John 5:17. This is talking about something different. This letter is adressing sins committed by people who are already saved–by Christians. What John is saying is that for followers of Jesus, there are sins which can be forgiven. In fact, from 1 John 1:5-7, if we walk in the light, his blood purifies us from ALL sin. However, also implied in 1 John 1:5-7, it is possible for us to lose our salvation. Hebrews 6:4-6 and Hebrews 10:26-31 describes the fact that deliberate, continual sin can lead to our losing our salvation. 1 John 5:16 implies that there IS a sin which leads to death. I believe that this is described by the two Hebrews passages quoted above. If you read all of 1 John, he is dealing with people who deny that Jesus is the Christ, and is warning disciples of Jesus to avoid such people. Yes, there is a sin which, for a saved person, can lead to their spiritual death. This is to sin in such a way that one falls away from God and that the Holy Spirit leaves such a person.