If anyone sees his brother sinning a sin which does not lead to death, he will ask, and He will give him life for those who commit sin not leading to death. There is sin leading to death. I do not say that he should pray about that. (NKJV)

This verse has confused many - what is the sin that leads to death and what is the sin that does not lead to death? Note first death he does not refer to the death of the body – physical death because all will die a physical death, then comes judgement. This verse concerns spiritual death, which concerns the annulment of the relationship between a person and God, that leads to judgement with hell as the final punishment (that gives rise to the “the dividing wall of hostility” spoken of in Ephesians 2:14). The first is obvious to the one who knows the gospel. Every person, a descendent of Adam, is tainted with sin (Romans 5:12) to the extent they will be judged and cast into hell (Romans 6:23). This is summarised in Ephesians 2:1-5.

The one who believes on the Lord Jesus Christ (e.g. John 3:16) will not die but live (John 11:25, 26). The sin that leads to death therefore is not believing that Christ is the Son of God, who died, was buried and rose again on the third day. Such a person is an unbeliever, and on death suffers. A believer is not immune to sin but is forgiven of all sin; see the Apostle Paul's dilemma in Romans 7. Thus, a believer cannot sin to the extent that he or she extinguishes the grace of God, which, if it was possible would lead to everlasting separation from God; but we know this is not possible because the Holy Spirit has seals a believer for eternal life. A believer is to pray for a sinning brother or sister in Christ – that is , we are to prayer for other believers. In regard unbelievers, the Bible does not request prayer, but rather believers are to preach the gospel message to that person. Paul writes: For "everyone who calls on the name of the Lord will be saved." How then will they call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching? (Romans 10:13-14)