Whoever remains in him doesn't sin. Whoever sins hasn't seen him, neither knows him.
Some Christians have used this verse to support the theory that Christians are sinless and perfect. Scripture and experience contradict this position (e.g., 1 John 1:8-9; et al.). Others have used it to teach that a Christian does not habitually sin, but this too is contrary to experience and the same Scripture. Advocates of this second view usually support it with the present tense of the Greek verb (harmartanei) that they take to mean "keeps on sinning."