Adam Clarke on 2 John 1:9

Whosoever transgresseth - Παραβαινων· He who passes over the sacred enclosure, or goes beyond the prescribed limits; and abideth not in the doctrine - does not remain within these holy limits, but indulges himself either in excesses of action or passion; hath not God for his Father, nor the love of God in his heart.

Hath both the father and the Son - He who abideth in the doctrine of Christ, his body is a temple of the Holy Trinity, and he has communion with the Father as his Father, and with the Son as his Savior and Redeemer.