"If anyone sees his brother committing a sin not leading to death, he shall ask and God will for him give life to those who commit sin not leading to death. There is a sin leading to death; I do not say that he should make request for this. All unrighteousness is sin, and there is a sin not leading to death." (1 John 5:16-17)This is a difficult verse to properly understand and to apply to our lives today. It's hard for us, or at least for me, to understand what kinds of sins John is talking about and our role in praying for them or not praying for them. It is tempting to think that John is speaking of the "unforgivable sin," where Jesus said, "Truly I say to you, all sins shall be forgiven the sons of men, and whatever blasphemies they utter; but whoever blasphemes against the Holy Spirit never has forgiveness, but is guilty of an eternal sin." (Mark 3:28-29) However, of the four Gospels, John omits these remarks of Jesus. It is hard to imagine that John would have refereed back to something he had never written. It is my opinion that this is not what John is referring to here,
The scriptures are clear as to the consequences of sin. God, speaking of how the son should not be held accountable for his father's offenses, says, "The soul who sins will die." (Ezekiel 18:4) Also, Paul reminds us of the price we pay for sin, saying, "For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord." (Romans 6:23) So, if the penalty for sin is death, then how can there be a sin not leading to death?
James reminds us that "we all stumble in many ways," (James 3:2) yet the promise of God is that, "When he falls, he will not be hurled headlong, because the Lord is the One who holds his hand." (Psalm 37:24) Furthermore, God, knowing that even the righteous will stumble and fall at times, says, "For a righteous man falls seven times, and rises again, but the wicked stumble in time of calamity." (Proverbs 24:16) We all, from time-to-time, stumble in our faith and revert to unrighteousness in our words and deeds. We forget our salvation and our deliverance from our former ways and former allegiances and belie the truth that we have been born again and translated into a Kingdom of light. We sin the sins of the past rather than living in the righteousness of the present. At times like these we need to be washed. It's not that we have lost our previous salvation, but we have been soiled by the world and our propensity to continue to live according to its ways. When Jesus washed His disciples feet, He said, "He who has bathed needs only to wash his feet, but is completely clean... You are already clean because of the word which I have spoken to you." (John 13:10, 15:3)
At times like these, whether in our own lives or in the life of someone else, we ought to pray or them and God will restore them and keep them in life abundant. God has given us the privilege of interceding on their behalf, to appropriate life for those who have stumbled into unrighteousness; to receive life from God for them on their behalf. However, when some have chosen a deliberate path of sin and have turned their backs on their faith, their restoration requires more than our prayers. While we should pray for their restoration, the life the seek will never be theirs until they return and make it right before God. Where in one case we might intercede for the stumbler to obtain from God, these must come to God themselves and intercede for their own sin and unrighteousness that they may be restored to forgiveness and fellowship with God. These have chosen a path leading to death and only an encounter with God will save them. While we pray for them, our prayers are not for pardon but for salvation; it's not for the continuation in life but the salvation from death.