The distinction between nonmortal and mortal sin might lead people to underestimate the seriousness of sin. Therefore John thinks fit to remind his readers of the fact that all wrongdoing is sin, that is, rebellion against God and siding with the devil (compare 3.4). Yet the distinction just made remains valid, as the next sentence of the verse makes clear; some evil deeds, although undoubtedly sins, do not lead to death and can be forgiven (compare 1.9-10).

All wrongdoing is sin, or ‘every evil/unrighteous deed is sin,’ ‘everyone who does wrong is sinning.’

But there is sin which is not mortal, or ‘yet not all sin is deadly sin,’ ‘yet not everyone who sins is sinning to death.’

Verses 18-20 contain an encouragement to the believers, made emphatic by the threefold repetition of the introductory we know; compare the threefold “I am writing” and “I write” in 2.12-14.

Quoted with permission from Haas, C., de Jonge, M. and Swellengrebel, J.L. A Handbook on The First Letter of John. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .