What does 1 John 5:16 mean?
John begins this verse with an odd topic: sin leading to death. The reference to "sins that do not lead to death" has caused much debate among interpreters. Some believe these words refer to spiritual death. Others believe John has in view physical death.The claim that this is a reference to spiritual death often comes from those who argue a person can lose his or her salvation. However, this appears to stand in stark contrast to verse 13. Instead, it is more likely that physical death is in view. Christians today often fail to realize the physical consequences of sin. This can range from criminal punishment to social shame to health issues. Christians are neither immune to sin nor to the consequences of sin. We are still subject to paying the earthly price for our choices.
This interpretation also makes better sense of the last comment of the verse. All disobedience to God is sin, and some disobedience can result in swift death. This may come by consequence, or by punishment. Ananias and Sapphira are an extreme example of this in action (Acts 5:1–11).
Here, Christians are explicitly told to pray for brothers and sisters whose sins are not that severe. According to this, God is particularly open to those kinds of requests. This same comment seems to suggest that prayers for more grievous sins are less likely to be answered. Note, however, that this verse does not say we should not pray for Christians caught in worse sins. Others have interpreted this as a reminder that prayers for the unbeliever, whose sins are still "leading to death," should focus on their salvation, not their sin.