The elder unto the elect lady and her children, whom I love in the truth; and not I only, but also all they that have known the truth; The elder - John the apostle, who was now a very old man, generally supposed to be about ninety, and therefore he uses the term ὁ πρεσβυτερος, presbyter or elder, not as the name of an office, but as designating his advanced age. He is allowed to have been the oldest of all the apostles, and to have been the only one who died a natural death.
This title led some of the ancients to attribute this epistle to a person called John the Presbyter, a member of the Church at Ephesus; and not to John the apostle. But this is a groundless supposition.
The elect lady - Εκλεκτῃ Κυρια· As Κυρια, kuria, may be the feminine of Κυριος, kurios, lord, therefore it may signify lady; and so several, both ancients and moderns, have understood it. But others have considered it the proper name of a woman, Kyria; and that this is a very ancient opinion is evident from the Peshito Syriac, the oldest version we have, which uses it as a proper name koureea, as does also the Arabic kooreea.
Some have thought that Eclecta was the name of this matron, from the word εκλεκτη, which we translate elect, and which here signifies the same as excellent, eminent, honorable, or the like. Others think that a particular Church is intended, which some suppose to be the Church at Jerusalem, and that the elect sister, 2 John 1:13, means the Church at Ephesus; but these are conjectures which appear to me to have no good ground. I am satisfied that no metaphor is here intended; that the epistle was sent to some eminent Christian matron, not far from Ephesus, who was probably deaconess of the Church, who, it is likely, had a Church at her house, or at whose house the apostles and traveling evangelists frequently preached, and were entertained. This will appear more probable in the course of the notes.
Whom I love in the truth - Whom I love as the Christian religion requires us to love one another.
And not I only - She was well known in the Churches; many had witnessed or heard of her fidelity, and partook of her hospitality; so that she had a good report of all Christians in that quarter.