1 John 2:8

Since this epistle is catholic, written generally to all, to both Jews and Gentiles, then with respect to the Jews it can be said that the apostle writes to them a commandment about love that is not new, but ancient. For on the tablets of …

By "commandment" John means the revelation of the dispensation. It cannot be called new with respect to God, but from the human point of view it was a mystery hidden in the Creator from the beginning.

The new dimension to the commandment is that now the light has come into the world, our Lord Jesus, because of whom the power of the devil has passed away.

Which is true in him and in you, etc. Behold here is the new, for darkness pertains to the old man and the light truly to the new man. Finally, the Apostle Paul says: Put off the old man and put on the new one …

It was exemplified in him, and is now fulfilled by you, in such a manner as it never was before. For there is no comparison between the state of the Old Testament believers, and that which ye now enjoy: the darkness of that dispensation is passed away; and Christ the true light now shineth in your hearts.

The more our darkness is past, and gospel light shines unto us, the deeper should our subjection be to the commandments of our Lord, whether considered as old or new. Light should produce a suitable heat. Accordingly, here is another trial of our Christian light; before, it was to be approved by obedience to God; here by Christian love.

Again, a new commandment I write unto you,.... Which is the same with the former, considered in different respects.

Joh 15:12. which thing is true in him and in you--"In Christ all things are always true, and were so from the beginning; but in Christ and in us conjointly the commandment [the love of brethren] is then true when we acknowledge the truth which is in Him, and have the same flourishing in us" [BENGEL].

Again, a new commandment I write unto you - “And yet, that which I write to you, and particularly enjoin on you, deserves in another sense to be called a new commandment, though it has been also inculcated from the beginning, for it was called new by the Saviour himself.” Or the meaning may be, “In addition to the general precepts which I have referred to, I do now call your attention to the new commandment of the Saviour, that which he himself called new.” There can be no doubt here that John refers to the commandment to “love one another,” (see 1Jn 2:9-11), and that it is here called new, not in the sense that John inculcated it as a novel doctrine, but in the sense that the Saviour called it such. For the reasons why it was so called by him, see the notes at Joh 13:34. Which thing is true in him - In the Lord Jesus. That is, which commandment or law of love was illustrated in him, or was manifested by him in his contact with his disciples. That which was most prominent in him was this very love which he enjoined on all his followers. And in you - Among you. That is, you have manifested it in your contact with each other. It is not new in the sense that you have never heard of it, and have never evinced it, but in the sense only that he called it new. Because the darkness is past, and the true light now shineth - The ancient systems of error, under which people hated each other, have passed away, and you are brought into the light of the true religion. Once you were in darkness, like others; now the light of the pure gospel shines around you, and that requires, as its distinguishing characteristic, love. Religion is often represented as light; and Christ spoke of himself, and was spoken of, as the Light of the world. See the notes at Joh 1:4-5. Compare Joh 8:12; Joh 12:35-36, Joh 12:46; Isa 9:2.