—1 John 5:16-17 (NASB)
This can be a tough verse because John doesn't specify which is a sin "leading to death" and which is "not leading to death". And it grabs our attention because John actually says not to pray for those committing a sin "leading to death"? As with all verses both difficult and easy, the number one rule for proper biblical interpretation is to always look at what other Scripture has to say. It's never a good thing to base a doctrine on a single verse, but on what the Bible has to say about a topic as a whole. So what we need to do is look for anything related in the rest of God's Word.