Expositor's Bible Commentary Commentary 2 John 1:9

"Whosoever goeth onward and abideth not in the teaching of Christ, hath not God: he that abideth in the teaching, the same hath both the Father and the Son." — 2 John 1:9 (ASV)

John’s second possibility is a more radical departure from the faith: “Anyone who goes too far” (better than NIV’s “Anyone who runs ahead”). The situation here implies not a loss of reward but of God himself, the loss or nonattainment of eternal life as promised in 1Jn 2:25.

The “teaching of Christ” can be construed as teaching about Christ or as the teaching that Christ himself did. The first option would be referring to the teaching that Jesus Christ has indeed come in the flesh. It is of little importance, however, which alternative is accepted, because the author holds equally to both positions. For Jesus Christ to be acknowledged as the one come in the flesh is fundamental to the faith, and for us to love one another (as taught by Jesus) is equally fundamental. To confess the former requires the latter. To have the Father and the Son is to have precisely what the false teachers have lost. To give up the Son is to lose the Father (cf. Jn 5:23; 14:6–7).