If we claim that we have not committed sins, we are [in effect] calling God a liar [i.e., because He says we have] and His word [i.e., the real truth about the matter] is not in our hearts.

however, it is really, in effect, a new commandment I write unto you, with respect to you: because the darkness is past, and things now appear in their true light.

He, that believeth on the Son of God, hath the witness in himself: he, that believeth not God, hath in effect made Him a liar, because he believed not the testimony which God hath testified of his Son.

And that testimony is to the effect that God has given us the Life of the Ages, and that this Life is in His Son.