And this is love,— That is, "the love which God the Father, by Christ his eternal Son, has enjoined upon Christians one towards another," as appears from the connection. The exhortations to mutual love among Christians, and the use of that phrase from the beginning, are so common in St. John's first epistle, that we need not refer to particular places. However, the parity between this and the first epistle appears remarkably in these instances.
Related Commentaries of 2 John 1:6
2 John 1:6
6 And this is love, that we walk after his commandments. This is the commandment, That, as ye have heard from the beginning, ye should walk in it.