Though the continued tradition of the church attests that this epistle came from John the apostle, yet we may observe some other evidence that will confirm (or with some perhaps even outweigh) the certainty of that tradition. It should seem that the penman was one of the apostolical college by the sensible palpable assurance he had of the truth of the Mediator’s person in his human nature: That which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, of the Word of life, 1 John 1:1. Here he takes notice of the evidence the Lord gave to Thomas of his resurrection, by calling him to feel the prints of the nails and of the spear, which is recorded by John. And he must have been one of the disciples present when the Lord came on the same day in which he arose from the dead, and showed them his hands and his side, John 20:20. But, that we may be assured which apostle this was, there is scarcely a critic or competent judge of diction, or style of argument and spirit, but will adjudge this epistle to the writer of that gospel that bears the name of the apostle John. They wonderfully agree in the titles and characters of the Redeemer: The Word, the Life, the Light; his name was the Word of God. Compare 1 John 1:1; 5:7; John 1:1; Rev. 19:13. They agree in the commendation of God’s love to us (1 John 3:1; 4:9; John 3:16), and in speaking of our regeneration, or being born of God, 1 John 3:9; 4:7; 5:1; John 3:5, 6. Lastly (to add no more instances, which may be easily seen in comparing this epistle with that gospel), they agree in the allusion to, or application of, that passage in that gospel which relates (and which alone relates) the issuing of water and blood out of the Redeemer’s opened side: This is he that came by water and blood, 1 John 5:6. Thus the epistle plainly appears to flow from the same pen as that gospel did. Now I know not that the text, or the intrinsic history of any of the gospels, gives us such assurance of its writer or penman as that ascribed to John plainly does. There (viz. John 21:24) the sacred historian thus notifies himself: This is the disciple that testifieth of these things and wrote these things; and we know that his testimony is true. Now who is this disciple, but he concerning whom Peter asked, What shall this man do? And concerning whom the Lord answered, If I will that he tarry till I come, what is that to thee? (John 21:22). And who (John 21:20) is described by these three characters:—1. That he is the disciple whom Jesus loved, the Lord’s peculiar friend. 2. That he also leaned on his breast at supper. 3. That he said unto him, Lord, who is he that betrayeth thee? As sure then as it is that that disciple was John, so sure may the church be that that gospel and this epistle came from the beloved John.
The epistle is styled general, as being not inscribed to any particular church; it is, as a circular letter (or visitation charge), sent to divers churches (some say of Parthia), in order to confirm them in their stedfast adherence to the Lord Christ, and the sacred doctrines concerning his person and office, against seducers; and to instigate them to adorn that doctrine by love to God and man, and particularly to each other, as being descended from God, united by the same head, and travelling towards the same eternal life.