What does 1 John 5:18 mean?

John's use of "we" in this letter is probably a reference to the apostles, but may also be a reference to the Christians to whom John is writing. As in 1 John 3:6 and 1 John 3:9, John here indicates that sin is never the result of fellowship with Christ. Believers can sin, but those sins are never the result of their walk with Jesus. The normal, expected state of a Christian's life is very different from that of an unbeliever. Temptation will continue to exist and even mature believers will struggle with sin (Romans 7). However, actively pursuing sin as a continual practice is not the mark of someone who has been changed by Christ.

The reference to being "protected" or "kept safe" is challenging to interpret. Some see "he who was born of God" in this verse as a reference to Jesus, but this is not a phrase used to describe Christ anywhere else by John. It has been interpreted to mean other believers, meaning other believers help protect a Christian through prayer and Satan cannot touch him (1 John 5:16–17). While both are possible, a more likely answer is that the phrase ought to be interpreted as "the one born of God keeps himself." In other words, just as John said in 1 John 3:9, walking closely with God means power against sin and temptation.