Adam Clarke's Commentary on the Bible

Verse 4 (1 John 2:4)

He that saith, I know him - This is a severe blow against those false teachers, and against all pretenders to religious knowledge, who live under the power of their sins; and against all Antinomians, and false boasters in the righteousness of Christ as a covering for their personal unholiness. They are all liars, and no truth of God is in them.

- Adam Clarke's Commentary on the Bible