1 John 5:17

All unrighteousness is sin A warning against carelessnessabout breaches of duty, whether in ourselves or in others. All such things are sin and need the cleansing blood of Christ (1 John 1:9; 1 John 2:2). Here, therefore, is a wide enough field for brotherly intercession. The statement serves also as a farewell declaration against the Gnostic doctrine that to the enlightened Christian declensions from righteousness involve no sin. Comp. the definition of sin as lawlessness in 1 John 3:4.

there is a sin not unto death Or, as before, there is sin not unto death: Wiclif, Tyndale, Cranmer, and the Genevan here omit the indefinite article, though they all insert it in 1 John 5:16. A warning against despair, whether about ourselves or about others. Not all sin is mortal: an answer by anticipation to the unchristian rigour of Montanism and Novatianism.