This verse contrasts the false and the true teachers.

Any one who goes ahead and does not abide in the doctrine of Christ: the two verbs are closely connected, the second explaining the first.

Goes ahead is used here in the unfavorable sense of ‘goes too far,’ ‘goes farther than one should.’ In some languages the meaning is better expressed in this context by a verb for ‘to go aside,’ or ‘to add.’

For abide in see comments on 1 John 2.10.

The doctrine of Christ should preferably be rendered as “the teaching of Christ.” This may mean “what Christ teaches” or “what is taught about Christ.” The former is preferable here; compare John 7.16-17. The reference is to what Christ told his followers about the will of God and the true way of life. For “to teach” and for “Christ” see comments on 1 John 2.27 and 22.

Several of the points just mentioned are illustrated in such renderings of the clause as ‘any one who goes so far that he does not observe what Christ taught,’ ‘any one who goes beyond the teaching of Christ by not keeping within it,’ ‘any one who does not keep to the teaching that is Christ’s, but goes aside from it (or adds to it).’

To have both the Father and the Son, or ‘to have the Father as well as the Son’: for the rendering of the verb in this context see 1 John 2.23. For the Father and the Son, see comments on 1 John 1.3 and 2.22.

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