Paul Chan Sermon - "Should Christians pray for everyone?"

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Pastor Paul Chan speaks on 1 John 5:13-17. It says: "If you see any brother or sister commit a sin that does not lead to death, you should pray and God will give them life. I refer to those whose sin does not lead to death. There is a sin that leads to death." 

Does this mean that the Bible doesn't' want us to pray for everyone? How can we determine what sin leads to death and what sin doesn't?