These words are an exhortation to hold fast, and not to forsake the doctrine of Christianity, which from the beginning they have received, and not to turn to novelties. Let that abide in you which ye have heard from the beginning; that is, from the first preaching of the gospel .
Note here, What is truth and true doctrine, namely, that which was delivered from the beginning. Truth is error's elder, though error is not much truth's younger.
Note, 2. By what means they received the evangelical doctrine, namely, by hearing let that which ye have heard abide in you, No sense more needful than that of hearing, for the benefit and advantage of man; both as he is by nature a reasonable creature, by converse a sociable creatue, and may be by grace a new creature; Faith cometh by hearing.
Note, 3. The duty required with reference to what they had heard; let that which ye have heard abide in you, namely, by a careful remembrance of it, and by resolute adherence to it. The sum of this exhortation is, that we retain and maintain the ancient catholic and apostolic faith; and verily when we consider how tenacious heretics are of their novel errors, it may bring a blush into our faces to consider how ready we are to be withdrawn from primitive truths.
Observe next, The motive with which our apostle doth enforce and back his exhortation If that which ye have heard remain in you, you shall continue in the Son, and in the Father; that is, in the love and favour of the Son, and of the Father, and in communion with both.
Quest. But why is the Son put before the Father here? Partly to insinuate, that the Son is no less in essencce and dignity than the Father, but equal in both; accordingly, the grace of our Lord Jesus Christ in the apostolical benediction, is mentioned before the love of God the Father: And partly, because no man cometh to, or continueth in the Father, but by the Son, He is the way, the truth, and the life.
The doctrine of the gospel comes from Christ; it leads to Christ, and by him unto the Father. If a man keep my word, we will make our abode with him. Joh_14:23