Book of 1 John Chapter 2 Vs. 8

 The New Commandment

1 John 2:8 “Again, a new commandment I write unto you, which thing is true in him and in you: because the darkness is past, and the true light now shineth.”

a new commandment... Greek: kainos, renewed; fresh (2Cor. 5:17). This new commandment is an old one renewed and made complete in meaning by Jesus Christ (1Jhn. 2:7-8; Lev. 19:18 with John 13:34).

New commandment

The commandment of love is both old and new. Old, because John's readers have had it from the beginning of their Christian experience. New, because, in the unfolding of Christian experience, it has developed new power, meaning, and obligation, and closer correspondence with the facts of Christ's life, with the crowning mystery of His passion, and with the facts of the Christian life.

Which thing is true (ὅ ἐστιν ἀληθὲς)

The expression which thing, or that which, refers either to the commandment of love, or to the fact stated, viz., that the old commandment is new. The fact that the old commandment is new is true in Him and in us. On the whole I prefer this.

This is just expressing how much easier it is for us to understand the law of God, since the Light of Jesus has shown on it. This new commandment is let Jesus, (the Light of the world), live in you and through you. We do not have to question about God anymore.

In Him and in us

For us, read you. The fact that the old commandment is new, is true in Him (Christ), since He gave it as a new commandment, and illustrated it by His word and example. It is true in you, since you did not receive it until Christ gave it, and since the person and life of Christ are appealing to you in new lights and with fresh power as your Christian life develops. In Him, points back to as He walked.

His perfect Light has shined in our heart and made us aware of His perfect Love. The Light of Jesus brightens our path that we are to walk. It is not a dark and fearful walk anymore.

Because

Explaining the apparent paradox.

The darkness (ἡ σκοτία)

See on John 1:5. God is light; and whatever is not in fellowship with God is therefore darkness. In all cases where the word is not used of physical darkness, it means moral insensibility to the divine light, moral blindness or obtuseness. Compare John 8:12; 12:35, 12:46; 1Jhn. 2:9, 2:11.

Is past (παράγεται)

Wrong. The passing is not represented as accomplished, but as in progress. Rev., rightly rendering the present tense, is passing away.

The true light (τὸ φῶς τὸ ἀληθινὸν)

Lit., the light, the true (light). See on that eternal life (1Jhn. 1:2). True, not as distinguished from false, but as answering to the true ideal. See on John 1:9. The true light is the revelation of God in Christ. See on 1Jhn. 1:5.

Shineth (φαίνει)

See on John 1:5. Compare Rev. 1:16; 8:12; 21:23; 2Pet. 1:19. See also Rom. 13:11 sqq.; Tit. 2:11; 3:4.

Yet Jesus had called that commandment new (John 13:34) and John pointed out that it had not lost its freshness. It is really still a new command, and its truth is seen in Him and you. This last assertion, somewhat freely rendered by NIV, seems to mean that the command to love came to realization first in Jesus Himself and then in His followers. The next phrase, because the darkness is passing and the true light is already shining, is best related back to the claim that he was after all writing a new command to them. His point was that the command to love which Jesus and His followers exhibit belongs to the new Age of righteousness which has begun to dawn. It does not belong to the old Age of darkness which was passing away. Christ’s Incarnation brought a light into the world which can never be extinguished. The love He manifested and taught His disciples to manifest is a characteristic of the Age to come. It is the darkness of the present world and all its hatred which is destined to disappear forever (cf. 1Jhn. 2:17).

In speaking this way, John gave to the terms light and darkness a slant differing slightly from what they had in 1Jhn. 1:1-10. There light was defined in terms of the fundamental character of God (1Jhn. 1:5). In that sense, the light has been shining as long as there has been a revelation of God to man. But here John wrote of the Incarnation in particular as the point at which the light began to shine. The new Age has dawned, and its true character can now be defined in terms of the special revelation God has made of Himself in His Son. And above all, that revelation is a revelation of divine love.